mm-
wmm * * * * * ;
7^
NOTICE OF INCORPORATION
United States Legal Document
J^" All citizens and residents are hereby advised that
this is a legally binding document duly incorporated by
reference and that failure to comply with such
requirements as hereby detailed within may subject you
to criminal or civil penalties under the law. Ignorance of
the law shall not excuse noncompliance and it is the
responsibility of the citizens to inform themselves as to
the laws that are enacted in the United States of America
and in the states and cities contained therein. "^&
* *
NBIC 2007, National Board Inspection Code,
Part 1, Installation, 2009 Addenda Release,
as mandated by the requirements of the States
of Alabama, Alaska, Arizona, Colorado, Iowa,
Kansas, Michigan, Missouri, Nebraska, New Jersey,
North Dakota, Ohio, Oregon, and Utah.
w i§**-* * * * i&KMmmxm
g^EEj|2E
National
Board
of boiler and
Pressure Vessel
Inspectors
Board
II C% «?■ •■: ■?- - ': ' ]f p . :' ;| ft
Code
Part 1 - Installation
NATIONAL BOARD INSPECTION CODE
NOTE: Pages ii through xvi are not part of this
American National Standard.
Library of Congress Catalog Card No. 52-44738
Printed in the United States of America
All Rights Reserved
©2009
The National Board of Boiler and Pressure Vessel Inspectors
Headquarters
1055 Crupper Avenue
Columbus, Ohio 43229-1 1 83
614.888.8320
614.847.1828 Fax
Testing Laboratory
7437 Pingue Drive
Worthington, Ohio 43085-1 71 5
614.888.8320
614.848.3474 Fax
Training & Conference Center
1 065 Crupper Avenue
Columbus, Ohio 43229-1 1 83
614.888.8320
614.847.5542 Fax
Inspection Training Center
1 075 Crupper Avenue
Columbus, Ohio 43229-1 1 83
614.888.8320
614.431.3208 Fax
NATIONAL BOARD INSPECTION CODE
The National Board of Boiler and Pressure Vessel Inspectors
Board of Trustees
R.J. Abenjr.
Chairman
J.T. Amato
First Vice Chairman
D.J. Jenkins
Second Vice Chairman
D.A. Douin
Seer eta ry Ureas urer
J.M. Given Jr.
Member at Large
G.L. Scribner
Member at Large
D.C. Price
Member at Large
B. Krasiun
Member at Large
Advisory Committee
G.W. Galanes, RE.
representing welding industries
E.J. Hoveke
representing National Board certificate holders
L.J. McManamon Jr.
representing organized labor
M.J. Pischke
representing pressure vessel manufacturers
B.R. Morelock, RE.
representing boiler and pressure vessel users
C.E. Perry
representing boiler manufacturers
C.G. Schaber
representing authorized inspection agencies (insurance companies)
NATIONAL BOARD INSPECTION CODE
National Board Members
Alabama Ralph P. Pate
Alaska Chris Fulton
Arizona Randall D.Austin
Arkansas Gary R. Myrick
California Donald C. Cook
Colorado Steve Nelson
Connecticut
Delaware James B. Harian
Flonda Michael A. Burns
Ceor g |a Paul J. Welch
Hawa " Keith A. Rudolph
ldaho MikePoulin
lllinois BennieF. Bailey
lndiana Dan Willis
lowa Michael Klosterman
Kansas Donald J. Jenkins
Kentucky Rodney Handy
Louisiana William Owens
Maine JohnH. Burpee
Maryland Karl J. Kraft
Massachusetts Edwards. Kawajr.
Michigan Robert J. Aben Jr.
Minnesota JoelT.Amato
Mississippi Kenneth L.Watson
Missouri Gary L. Scribner
Montana Timothy Stewart
Nebraska Christopher B. Cantrell
Nevada R oy L p erry
New Hampshire Wayne Brigham
New Jersey Milton Washington
NewVbrk Peter L. Vescio Jr.
North Carolina Jack M. Given Jr.
North Dakota Robert Reetz
Ohio DeanT. Jagger
Oklahoma Tom Monroe
Oregon Michael D.Graham
Pennsylvania Jack A. Davenport
Rhode Island Benjamin Anthony
South Carolina Ronald W. Spiker
South Dakota Howard D. Pfaff
Tennessee Audrey E. Rogers
Texa s Anthony P. Jones
Utah Rick K.Sturm
Vermont Wesley E. Crider Jr.
Virginia Edward G. Hilton
Washington Linda Williamson
West Virginia John F. Porcella
Wisconsin Michael J. Verhagen
Chicago, IL Michael J. Ryan
Detroit, Ml John E. Bell
Los Angeles, CA JovieAclaro
Milwaukee, Wl Randal S. Pucek
New York, NY William McGivney
Alberta Ken K.T Lau
British Columbia John G. Siggers
Manitoba Terry W Rieger
New Brunswick Dale E. Ross
Newfoundland & Labrador E. Dennis Eastman
Northwest Territories Steve Donovan
Nova Scotia Peter Dodge
Nunavut Territory
Ontario Gilles Lemay
Prince Edward Island Kenneth Hynes
Quebec Madiha M. Kotb
Saskatchewan Brian Krasiun
Yukon Territory Daniel C. Price
NATIONAL BDARD INSPECTION CODE
National Board Inspection Code Committees
Main Committee
T. Parks, Chair
The National Board of Boiler and
Pressure Vessel Inspectors
J. Pillow
Common Arc Corporation
R. Wielgoszinski, Vice Chair
Hartford Steam Boiler Inspection and
Insurance Company of Connecticut
R. Reetz
State of North Dakota
R. Hough, Secretary
The National Board of Boiler and
Pressure Vessel Inspectors
H. Richards
Southern Company
S. Bacon
Conoco Phillips-Ferndale Refinery
J. Richardson
Consultant-Dresser, Inc.
P. Bourgeois
Travelers
G. Scribner
State of Missouri
D. Canonico
Canonico & Associates
J. Sekely
Wayne Crouse Inc.
D. Cook
State of California
R. Snyder
ARISE, Inc.
P. Edwards
Stone & Webster, Inc.
S. Staniszewski
US Department of Transportation
C. Calanes
Midwest Generation EME, LLC
R. Sulzer
The Babcock & Wilcox Company
J. Given
State of North Carolina
H. Titer
MIRANT Mid-Atlantic
F. Hart
Furmanite Corporation
J. Yagen
Dynegy, Inc.
C. Hopkins
Seattle Boiler Works
D. Parrish
FM Global
NATIONAL BOARD INSPECTION CODE
Subcommittee for Installation (Part 1)
H. Richards, Chair
Southern Company
C. Hopkins
Seattle Boiler Works
P. Bourgeois
Travelers
C. Halley
ABMA
S. Konopacki
Midwest Generation
B. Moore
Hartford Steam Boiler Inspection and
Insurance Company of Connecticut
H.Tyndall
Zurich Services Corp.
C. Scribner
State of Missouri
R. Snyder
ARISE, Inc.
R. Sulzer
The Babcock & Wilcox Company
H. Titer
MIRANT Mid-Atlantic
J. Yagen
Dynegy, Inc.
Subgroup for Installation (Part 1)
Boilers
Pressure Vessels and Piping
C. Hopkins, Chair
Seattle Boiler Works
J. Yagen, Chair
Dynegy, Inc.
P. Bourgeois
H. Richards
St. Paul Travelers
Southern Company
G. Halley, RE.
G. Scribner
ABMA
State of Missouri
S. Konopacki
Midwest Generation
R. Snyder
ARISE, Inc.
B. Moore, P.E.
H. Titer
Hartford Steam Boiler Inspection
MIRANT Mid-Atlantic
H.Tyndall
H.Tyndall
Zurich Services Corp.
Zurich Services Corp.
G. Scribner
State of Missouri
R. Sulzer
The Babcock & Wilcox Company
VI
NATIONAL BOARD INSPECTION CODE
Subcommittee for Inspection (Part 2)
D. Cook, Chair
State of California
S. Bacon
Conoco Phillips-Femdale Refinery
D. Canonico
Canonico & Associates
). Getter
Worthington Cylinders
C. McRae
Trinity Industries, Inc.
V. Newton
Chubb & Son
T. Barker
FM Global
M. Horbaczewski
Midwest Generation
D. Parrish
FM Global
R. Reetz
State of North Dakota
J. Richardson
Consultant-Dresser, Inc.
J. Riley
Chevron Energy and Technology
M. Schwartzwalder
AEP
S. Staniszewski
US Department of Transportation
R. VVacker
Dupont
M. Mooney
Liberty Mutual Insurance
Subgroup for Inspection (Part 2)
General Requirements
J. Getter, Chair
Worthington Cylinders
D. Canonico
Canonico & Associates
R. Dobbins
Zurich N.A.
M. Horbaczewski
Midwest Generation
D. Parrish
FM Global
J. Richardson
Consultant-Dresser, Inc.
S pecific Requirements
S. Staniszewski
US Department of Transportation
S. Bacon
Conoco Phillips-Femdale Refinery
D. Cook
State of California
R. Dobbins
Zurich N.A.
J. Getter
Worthington Cylinders
G. McRae
Trinity Industries, Inc.
J. Riley
Chevron Energy and Technology
M. Schwartzwalder
AEP
R. Wacker
Dupont
VII
NATIONAL BOARD INSPECTION CODE
Subcommi ttee for Repairs and Alterations (Part 3)
G. Calanes, Chair
Midwest Generation EME, LLC
P. Edwards
Stone & Webster, Inc.
J. Given
State of North Carolina
Wayne Jones
Arise, Inc.
J. Larson
OneBeacon America Insurance Company
F. Paviovicz
The Babcock & Wilcox Company
J. Pillow -Vice Chair
Common Arc Corporation
B. Schulte
NRG Texas, LP
J. Sekely
Wayne Crouse Inc.
M. Webb
Xcel Energy
Subgr oup for Rep airs and Alterations (Part 3)
General Requirements
P. Edwards, Chair
Stone & Webster, Inc.
J. Larson
One Beacon America Insurance Company
R. Pulliam
The Babcock & Wilcox Company
8. Schulte
NRG Texas, LP
M. Webb
Xcel Energy
B. Boseo
Alstom/AP ComPower Inc.
Brian Morelock
Eastman Chemical
S pecific Req uirements
J. Sekely
Wayne Crouse Inc.
G. Galanes
Midwest Generation EME, LLC
J. Given
State of North Carolina
W. Jones
ARISE, Inc.
F. Paviovicz
The Babcock & Wilcox Company
J. Pillow, Chair
Common Arc Corporation
B. Boseo
Alstom/AP ComPower Inc.
Michael Huffman
American Welding & Tank
NATIONAL BOARD INSPECTION CODE
Subcommittee for Pressure Relief Devices (Parts 1, 2, and 3)
F. Hart, Chair
Furmanite America Inc.
R. Donalson
Tyco Valves and Controls
A. Cox
Industrial Value
K. Fitzsimmons
Carter Chambers, LLC
J. Ball
The National Board of Boiler and
Pressure Vessel Inspectors
G. Humphries
Oxy Vinyls, LP
M. Brodeur
International Valve & Instr. Corp.
R. McCaffrey
Quality Valve
S. Cammeresi
CCR
T. Patel
Farris Engineering
D. DeMichael
DuPont
Special Subgroups for Installation, Inspection, and Repairs and Alterations (Parts 1, 2, and 3)
Locomotive Boilers
B. Withuhn, Chair
Smithsonian Institution
S. Lee
Union Pacific Railroad
S. Butler
Midwest Locomotive & Machine
Works
D. McCormack
Consultant
D. Conrad
Valley Railroad Co.
L. Moedinger
Strasburg Railroad
R. Franzen
Steam Services of America
R. Reetz
State of North Dakota
D. Griner
Wasatch Railroad Contractors
G. Scerbo
Federal Railroad Administration
S. Jackson
D&SNG
R. Schueler
The National Board of Boiler and Pres-
sure Vessel Inspectors
M. Janssen
Vapor Locomotive Company
R. Stone
ABB/Combustion Engineering
R.Yuill
Consultant
Historica! Boilers
R. Reetz, Chair
State of North Dakota
D. Cook
State of California
T. Dillion
Deltak
B. Babcock
Consultant
M. Wahl
WHSEA
D. Rupert
Consultant
J. Larson
One Beacon America Insurance
Company
S. Bacon
Conoco Phillips-Ferndale Refinery
F. Johnson
PCS Phosphate
IX
NATIONAL BOARD INSPECTION CODE
Special Subgroups for Installation,
Inspection, and Repairs and Alterations (Parts 1, 2, and 3)
Graphite
Fiber-Reinforced Pressure Vessels
E. Soltow, Chair
SCL Carbon Croup/SCL Technic
B. Shelley, Chair
DuPont
W. Banker
Graphite Repairs, Inc
F. Brown
The National Board of Boiler and
Pressure Vessel Inspectors
F. Brown
The National Board of Boiler and
Pressure Vessel Inspectors
J. Bustillos
Bustillos and Consultants
K. Cummins
Louisville Graphite
D. Eisberg
Energy Recovery Inc.
S. Malone
Carbone of America
T. Fowler
Retired/Spicewood, TX
M. Minick
One CIS Insurance
D. Keeler
The Dow Chemical Company
A. Stupica
SCL Carbon Group/SGL Technic
R. Lewandowski
Corrosion Resistant Composites
T. Bonn
Carbone of America
H. Marsh
Consultant
J. Richter
FEMech Engineering
D. Cook
State of California
N. Newhouse
Lincoln Composites
D. Hodgkinson
Consultant
M. Gorman
Digital Wave
R. Crawford
L&M Fiberglass
T. Cowley
Dupont
NATIONAL BOARD INSPECTION CODE
National Board Inspection Code
2007 Edition including 2008 and 2009 Addendum
Date of Issue — December 31, 2009
This code was developed under procedures accredited as meeting the criteria for American
National Standards. The Consensus Committee that approved the code was balanced to ensure
that individuals from competent and concerned interests had an opportunity to participate. The
proposed code was made available for public review and comment, which provided an
opportunity for additional public input from industry, academia, regulatory and jurisdictional
agencies, and the public-at-large.
The National Board does not "approve," "rate," or "endorse" any item, construction,
proprietary device, or activity.
The National Board does not take any position with respect to the validity of any patent rights
asserted in connection with any items mentioned in this document, and does not undertake
to insure anyone utilizing a standard against liability for infringement of any applicable Letters
Patent, nor assume any such liability. Users of a code are expressly advised that determination
of the validity of any such patent rights, and the risk of infringement of such rights, is entirely
their own responsibility.
Participation by federal agency representative(s) or person(s) affiliated with industry is not to be
interpreted as government or industry endorsement of this code.
The National Board accepts responsibility for only those interpretations issued in accordance
with governing National Board procedures and policies that preclude the issuance of
interpretations by individual committee members.
The footnotes in this document are part of this American National Standard.
M
f\R
R
w
®
The above National Board symbols are registered with the US Patent Office.
"National Board" is the abbreviation for The National Board of Boiler and Pressure Vessel
Inspectors.
No part of this document may be reproduced in any form, in an electronic retrieval system or
otherwise, without the prior written permission of the publisher.
NATIONAL BOARD INSPECTION CODE
XII
NATIONAL BOARD INSPECTION CODE
Foreword
The National Board of Boiler and Pressure Vessel Inspectors is an organization comprised of
Chief Inspectors for the states, cities, and territories of the United States and provinces and
territories of Canada. It is organized for the purpose of promoting greater safety to life and
property by securing concerted action and maintaining uniformity in post-construction
activities of pressure-retaining items, thereby ensuring acceptance and interchangeability
among Jurisdictional authorities responsible for the administration and enforcement of various
codes and standards.
In keeping with the principles of promoting safety and maintaining uniformity, the National
Board originally published The NBIC in 1946, establishing rules for inspection and repairs to
boilers and pressure vessels. The National Board Inspection Code (NBIC) Committee is charged
with the responsibility for maintaining and revising the NBIC. In the interest of public safety,
the NBIC Committee decided, in 1 995, to revise the scope of the NBIC to include rules for
installation, inspection, and repair or alteration to boilers, pressure vessels, piping, and
nonmetallic materials.
In 2007, the NBIC was restructured into three Parts specifically identifying important post-
construction activities involving safety of pressure-retaining items. This restructuring provides for
future expansion, transparency, and uniformity, ultimately improving public safety.
The NBIC Committee's function is to establish rules of safety governing post-construction activities
for the installation, inspection and repair and alteration of pressure-retaining items, and to interpret
these rules when questions arise regarding their intent. In formulating the rules, the NBIC
Committee considers the needs and concerns of individuals and organizations involved in the
safety of pressure-retaining items. The objective of the rules is to afford reasonably certain
protection of life and property, so as to give a reasonably long, safe period of usefulness.
Advancements in design and material and the evidence of experience are recognized.
The rules established by the NBIC Committee are not to be interpreted as approving,
recommending, or endorsing any proprietary or specific design, or as limiting in any way an
organization's freedom to choose any method that conforms to the NBIC rules.
The NBIC Committee meets regularly to consider revisions of existing rules, formulation of new
rules, and respond to requests for interpretations. Requests for interpretation must be addressed
to the NBIC Secretary in writing and must give full particulars in order to receive Committee
consideration and a written reply. Proposed revisions to the Code resulting from inquiries will
be presented to the NBIC Committee for appropriate action.
Proposed revisions to the Code approved by the NBIC Committee are submitted to the
American National Standards Institute and published on the National Board Web site to
invite comments from all interested persons. After the allotted time for public review and final
approval, revisions are published annually in Addenda to the NBIC.
Organizations or users of pressure-retaining items are cautioned against making use of
revisions that are less restrictive than former requirements without having assurance that they
have been accepted by the Jurisdiction where the pressure-retaining item is installed.
XIII
NATIONAL BOARD INSPECTION CODE
The general philosophy underlying the NBIC is to parallel those provisions of the original code
of construction, as they can be applied to post-construction activities.
The NBIC does not contain rules to cover all details of post-construction activities. Where
complete details are not given, it is intended that individuals or organizations, subject to the
acceptance of the Inspector and Jurisdiction when applicable, provide details for post-
construction activities that will be as safe as otherwise provided by the rules in the original
Code of Construction.
Activities not conforming to the rules of the original code of construction or the NBIC must
receive specific approval of the Jurisdiction, who may establish requirements for design,
construction, inspection, testing, and documentation.
There are instances where the NBIC serves to warn against pitfalls; but the Code is not a hand-
book, and cannot substitute for education, experience, and sound engineering judgment.
It is intended that this Edition of the NBIC and any subsequent Addenda not be retroactive.
Unless the Jurisdiction imposes the use of an earlier edition, the latest effective edition and
addenda is the governing document.
NATIONAL BOARD INSPECTION CODE
Introduction
It is the purpose of the National Board Inspection Code (NBIC) to maintain the integrity of
pressure-retaining items by providing rules for installation, and after the items have been
placed into service, by providing rules for inspection and repair and alteration, thereby
ensuring that these items may continue to be safely used.
The NBIC is intended to provide rules, information and guidance to manufacturers,
Jurisdictions, inspectors, owner-users, installers, contractors, and other individuals and
organizations performing or involved in post-construction activities, thereby encouraging the
uniform administration of rules pertaining to pressure-retaining items.
Scope
The NBIC recognizes three important areas of post-construction activities where information,
understanding, and following specific requirements will promote public and personal safety.
These areas include:
• Installation
• Inspection
• Repairs and Alterations
The NBIC provides rules, information, and guidance for post-construction activities, but does
not provide details for all conditions involving pressure-retaining items. Where complete de-
tails are not provided in this Code, the Code user is advised to seek guidance from the Jurisdic-
tion and from other technical sources.
The words shall, should, and may are used throughout the NBIC and have the following intent:
• Shall - action that is mandatory and required.
9 Should - indicates a preferred but not mandatory means to accomplish the requirement
unless specified by others such as the Jurisdiction.
9 May - permissive, not required or a means to accomplish the specified task.
Organization
The NBIC is organized into three Parts to coincide with specific post-construction activities
involving pressure-retaining items. Each Part provides general and specific rules, information,
and guidance within each applicable post-construction activity. Other NBIC Parts or other
published standards may contain additional information or requirements needed to meet the
rules of the NBIC. Specific references are provided in each Part to direct the user where to find
this additional information. NBIC Parts are identified as:
• Part 1, Installation -This Part provides requirements and guidance to ensure all types of
pressure-retaining items are installed and function properly. Installation includes
meeting specific safety criteria for construction, materials, design, supports, safety
devices, operation, testing, and maintenance.
• Part 2, Inspection -This Part provides information and guidance needed to perform and
document inspections for all types of pressure-retaining items. This Part includes
information on personnel safety, non-destructive examination, tests, failure
mechanisms, types of pressure equipment, fitness for service, risk-based assessments,
and performance-based standards.
xv
NATIDNAL BOARD INSPECTION CODE
• Part 3, Repairs and Alterations -This Part provides information and guidance to
perform, verify, and document acceptable repairs or alterations to pressure-retaining
items regardless of code of construction. Alternative methods for examination, testing,
heat treatment, etc., are provided when the original code of construction requirements
cannot be met. Specific acceptable and proven repair methods are also provided.
Each NBIC Part is divided into major Sections as outlined in the Table of Contents.
Tables, charts, and figures provide relevant illustrations or supporting information for text
passages, and are designated with numbers corresponding to the paragraph they illustrate or
support within each Section. Multiple tables, charts, or figures referenced by the same
paragraph will have additional letters reflecting the order of reference. Tables, charts, and
figures are located in or after each major Section within each NBIC Part.
Text Identification and Numbering
Each page in the text will be designated in the top header with the publication's name, part
number, and part title. The numbering sequence for each section begins with the section
number followed by a dot to further designate major sections (e.g., 1 .1 , 1 .2, 1 .3). Major
sections are further subdivided using dots to designate subsections within that major section
(e.g., 1 .1 .1, 1 .2.1, 1 .3.1). Subsections can further be divided as necessary.
Paragraphs under sections or subsections shall be designated with small letters in parenthesis
(e.g., a), b), c)) and further subdivided using numbers in parenthesis (e.g., 1), 2), 3)).
Subdivisions of paragraphs beyond this point will be designated using a hierarchical sequence
of letters and numbers followed by a dot.
Example: 2.1 Major Section
2.1.1 Section
2.1.2 Section
2.1.2. Subsection
a) paragraph
b) paragraph
1) subparagraph
2) subparagraph
a. subdivisions
1. subdivisions
2. subdivisions
b. subdivisions
1. subdivisions
2. subdivisions
Tables and figures will be designated with the referencing section or subsection identification.
When more than one table or figure is referenced in the same section or subsection, letters or
numbers in sequential order will be used following each section or subsection identification.
XVI
NATIONAL BOARD INSPECTION CODE
Supplements
Supplements are contained in each Part of the NBIC to designate information only pertaining to
a specific type of pressure-retaining item (e.g., Locomotive Boilers, Historical Boilers, Graphite
Pressure Vessels.) Supplements follow the same numbering system used for the main text only
preceded by the Letter "S." Each page of the supplement will identify the supplement number
and name in the top heading.
Addenda
Addenda, which include revisions and additions to this Code, are published annually. Addenda
are permissive on the date issued and become mandatory six months after the date of issue.
The addenda will be sent automatically to purchasers of the Code up to the publication of the
next edition. Every three years the NBIC is published as a new edition that includes that year's
addenda.
Interpretations
On request, the NBIC Committee will render an interpretation of any requirement of this Code.
Interpretations are provided for each Part and are specific to the Code edition and addenda
referenced in the interpretation. Interpretations provide information only and are not part of
this Code.
Jurisdictiona! Precedence
Reference is made throughout this Code to the requirements of the "Jurisdiction." Where any
provision herein presents a direct or implied conflict with any jurisdictional regulation, the
jurisdictional regulation shall govern.
Units of Measurement
Both U.S. customary units and metric units are used in the NBIC. The value stated in U.S. custom-
ary units or metric units are to be regarded separately as the standard. Within the text, the met-
ric units are shown in parentheses. In supplement 6, Continued Service and Inspection of DOT
Transport Tanks, the metric units are shown first with the U.S. customary units shown in parentheses.
U.S. customary units or metric units may be used with this edition of the NBIC, but one system
of units shall be used consistently throughout a repair or alteration of pressure-retaining items.
It is the responsibility of National Board accredited repair organizations to ensure the
appropriate units are used consistently throughout all phases of work. This includes materials,
design, procedures, testing, documentation, and stamping. The NBIC policy for metrication is
outlined in each part of the NBIC.
Accreditation Programs
The National Board administers and accredits three specific repair programs 1 as shown below:
"R" Repairs and Alterations to Pressure-Retaining Items
"VR" Repairs to Pressure Relief Valves
"NR" Repair and Replacement Activities for Nuclear Items
1 Caution, some Jurisdictions may independently administer a program of authorization for organizations to perform repairs and
alterations within that Jurisdiction.
XVII
NATIONAL BOARD INSPECTION CODE
Part 3, Repairs and Alterations, of the NBIC describes the administrative requirements for the
accreditation of these repair organizations.
The National Board also administers and accredits four specific inspection agency programs as
shown below:
New Construction
Criteria for Acceptance of Authorized Inspection Agencies for New Construction
(NB-360)
Inservice
Qualifications and Duties for Authorized Inspection Agencies (AlAs) Performing Inservice
Inspection Activities and Qualifications for Inspectors of Boilers and Pressure Vessels
(NB-369)
Owner-User
Accreditation of Owner-User Inspection Organizations (OUIO) (NB-371 ) Owners or users
may be accredited for both a repair and inspection program provided the requirements
for each accreditation program are met.
Federal Government
Qualifications and Duties for Federal Inspection Agencies Performing Inservice Inspection
Activities (FIAs) (NB-390) " " '
These programs can be viewed on the National Board Web site. For questions or further infor-
mation regarding these programs contact:
The National Board of Boiler and Pressure Vessel Inspectors
1055 Crupper Avenue
Columbus, OH 43229-1 183
Phone — 614.888.8320
Fax — 614.847.1828
Web site — www.nationalboard.org
Certificates of Authorization for Accreditation Programs
Any organization seeking an accredited program may apply to the National Board to obtain a
Certificate of Authorization for the requested scope of activities. A confidential review shall be
conducted to evaluate the organization's quality system. Upon completion of the evaluation,
a recommendation will be made to the National Board regarding issuance of a Certificate of
Authorization.
Certificate of Authorization scope, issuance, and revisions for National Board accreditation
programs are specified in the applicable National Board procedures. When the quality system
requirements of the appropriate accreditation program have been met, a Certificate of
Authorization and appropriate National Board symbol stamp shall be issued.
XVIII
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
2.6.3 Drains 21
2.6.3.1 Connection 21
2.6.3.2 Pressure Rating 22
2.6.3.3 Parts 22
2.7 Operating Systems 22
2.7.1 Breeching and Dampers 22
2.7.2 Burners and Stokers 22
2.7.3 Steam Supply 22
2.7.4 Condensate and Return 23
2.7.5 Blowoff 23
2.8 Controls and Gages 24
2.8.1 Water " 24
2.8.2 Pressure Gage 26
2.8.2.1 Connection 26
2.8.3 Temperature 26
2.9 Pressure Relief Valves 26
2.9.1 Valve Requirements — General 26
2.9.1.1 Number 26
2.9.1.2 Location 27
2.9.1.3 Capacity 27
2.9.1.4 Set Pressure 29
2.9.2 Forced-Flow Steam Generator 29
2.9.3 Superheaters 30
2.9.4 Economizers 30
2.9.5 Pressure Reducing Valves 30
2.9.6 Mounting and Discharge Requirements 31
2.10 Testing and Acceptance 32
2.10.1 General 32
2.10.2 Pressure Test 32
2.10.3 Nondestructive Examination 32
2.10.4 System Testing 32
2.10.5 Final Acceptance 32
2.10.6 Boiler Installation Report 32
Section 3 Steam Heating Boilers, Hot-Water Heating Boilers, Hot-Water Supply
Boilers, and Potable Water Heaters 33
3.1 Scope 34
3.2 Definitions 34
3.2.1 Steam Heating Boilers 34
3.2.2 Hot-Water Heating and Hot-Water Supply Boilers 34
3.2.3 Potable Water Heaters 34
3.3 General Requirements 34
3.3.1 Supports 34
3.3.1.1 Methods of Support for Steam Heating,
Hot-Water Heating, and Hot-Water Supply Boilers 34
3.3.2 Settings 35
3.3.3 Structural Steel 36
3.3.4 Clearances 37
3.4 Boiler Room Requirements 37
3.4.1 Exit 37
3.4.2 Ladders and Runways 37
3.5 Source Requirements 38
3.5.1 Water 38
3.5.2 Fuel 38.
3.5.3 Electrical 38
3.5.4 Ventilation and Combustion Air 39
3.5.5 Lighting 39
3.5.6 Emergency Valves and Controls 39
3
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
3.6 Discharge Requirements 39
3.6.1 Chimney or Stack 39
3.6.2 Ash Removal 40
3.6.3 Drains 40
3.7 Operating Systems 40
3.7.1 Oil Heaters 40
3.7.2 Breeching and Dampers 40
3.7.3 Burners and Stokers 40
3.7.4 Feedwater, Makeup Water, and Water Supply 40
3.7.5 Stop Valves 41
3.7.5.1 Steam Heating, Hot-Water Heating, and
Hot-Water Supply Boilers 41
3.7.5.2 Potable Water Heaters 41
3.7.6 Return Pipe Connections 41
3.7.7 Bottom Blowoff and Drain Valves 46
3.7.7.1 Steam Heating, Hot-Water Heating, and
Hot-Water Supply Boilers 46
3.7.7.2 Potable Water Heaters 46
3.7.8 Modular Steam Heating and Hot-Water Heating Boilers 47
3.7.8.1 Individual Modules 47
3.7.8.2 Assembled Modular Boilers 47
3.7.9 Provisions for Thermal Expansion 47
3.7.9.1 Expansion Tanks and Piping for Steam Heating,
Hot-Water Heating, Hot-Water Supply Boilers, and
Potable Water Heaters 47
3.7.9.2 Expansion Tanks and Piping For Potable Water Heaters 49
3.8 Instruments, Fittings, and Controls 50
3.8.1 Steam Heating Boilers 50
3.8.1.1 Steam Gages 50
3.8.1 .2 Water Gage Glasses 50
3.8.1.3 Water Column and Water Level Control Pipes 51
3.8.1 .4 Pressure Control 51
3.8.1 .5 Automatic Low-Water Fuel Cutoff and/or Water
Feeding Device 51
3.8.1 .6 Modular Steam Heating Boilers 52
3.8.1 .7 Instruments, Fittings, and Controls Mounted Inside
Boiler Jackets 52
3.8.2 Hot-Water Heating or Hot-Water Supply Boilers 52
3.8.2.1 Pressure or Altitude Gages 52
3.8.2.2 Thermometers 52
3.8.2.3 Temperature Control 53
3.8.2.4 Low-Water Fuel Cutoff 53
3.8.2.5 Modular Hot-Water Heating Boilers 53
3.8.2.6 Instruments, Fittings, and Controls Mounted Inside
Boiler Jackets 53
3.8.3 Potable Water Heaters 54
3.8.3.1 Temperature Controls 54
3.8.3.2 Thermometer 54
3.9 Pressure-Relieving Valves 54
3.9.1 Safety Valve Requirements — General 54
3.9.1 .1 Mounting Safety and Safety ReliefValves for
Steam Heating, Hot-Water Heating, and
Hot-Water Supply Boilers 54
3.9.1 .1 .1 Permissible Mounting 54
3.9.1 .1 .2 Requirements for Common Connections
for Two or More Valves 54
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
3.9.1.2 Threaded Connections 55
3.9.1.3 Prohibited Mountings 55
3.9.1 .4 Use of Shutoff Valves Prohibited 55
3.9.1 .5 Safety and Safety ReliefValve Discharge Piping 55
3.9.1 .6 Temperature and Pressure Safety Relief Valves 55
3.9.2 Safety Valve Requirements for Steam Boilers 55
3.9.3 Safety ReliefValve Requirements for Hot-Water Heating or
Hot-Water Supply Boilers 57
3.9.4 Safety ReliefValve Requirements for Potable Water Heaters 58
3.9.4.1 Installation 58
3.9.4.2 Permissible Mountings 58
3.9.4.3 Requirements for Common Connection for Two
or More Valves 59
3.9.4.4 Threaded Connections 59
3.9.4.5 Prohibited Mountings 59
3.9.4.6 Use of Shutoff Valves Prohibited 59
3.9.4.7 Safety ReliefValve Discharge Piping 59
3.9.5 Safety and Safety ReliefValves for Tanks and Heat Exchangers 59
3.9.5.1 Steam to Hot-Water Supply 59
3.9.5.2 High-Temperature Water to Water Heat Exchanger 59
3.9.5.3 High-Temperature Water to Steam Heat Exchanger 60
3.10 Testing and Acceptance 60
3.10.1 Pressure Test 60
3.10.2 Final Acceptance 60
3.10.3 Boiler Installation Report 60
3.10.4 Tables and Figures 60
Section 4 Pressure Vessels 63
4.1 Scope 64
4.2 Definitions 64
4.3 General Requirements 64
4.3.1 Supports 64
4.3.2 Clearances 64
4.3.3 Piping 64
4.3.4 Bolting 64
4.4 Instruments and Controls 64
4.4.1 Level Indicating Devices 64
4.4.2 Pressure Indicating Devices 65
4.5 Pressure Relief Devices 65
4.5.1 Device Requirements 65
4.5.2 Number of Devices 65
4.5.3 Location 65
4.5.4 Capacity 65
4.5.5 Set Pressure 66
4.5.6 Installation and Discharge Piping Requirements 66
4.6 Testing and Acceptance 67
Section 5 Piping 69
5.1 Scope 70
5.2 General Requirements 70
5.2.1 Additions to Existing Piping 70
5.2.2 Proximity to Other Equipment and Structures 70
5.2.3 Flanges and Other Non-Welded Joints 70
5.2.4 Valves 70
5.2.5 Materials 71
5.2.6 Hangers and Supports 71
5.2.7 Protection and Cleaning 71
5
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
5.2.8 Welding and Brazing 71
5.2.9 Bolting 71
5.3 Pressure Relief Devices 71
5.3.1 Device Requirements 71
5.3.2 Number of Devices 71
5.3.3 Location 72
5.3.4 Capacity 72
5.3.5 Set Pressure 72
5.3.6 Inlet and Discharge Piping Requirements 72
5.4 Examination, Inspection, and Testing 73
Section 6 Supplements 75
5.1 Installation of Yankee Dryers (Rotating Cast-iron Pressure Vessels)
with Finished Shell Outer Surfaces 76
51.1 Scope 76
51.2 Assessment of Installation 76
51.3 Determination of Allowable Operating Parameters 78
51 .4 ASME Code Primary Membrane Stress Criteria 80
51 .5 Pressure Testing 80
51 .6 Nondestructive Examination 81
5.2 Safety Valves on the Low-Pressure Side of Steam Pressure-Reducing Valves 82
52.1 Scope 82
52.2 Safety Valve Capacity 82
52.3 Calculation of Safety Valve Relieving Capacity 82
52.4 Steam Flow When Flow Coefficients Are Not Known 83
52.5 Two-Stage Pressure-Reducing Valve Stations 87
Section 7 NBIC Policy for Metrication 89
7.1 General 90
7.2 Equivalent Rationale 90
7.3 Procedure for Conversion 90
7.4 Referencing Tables 91
Section 8 Preparation of Technical Inquiries to the National Board
Inspection Code Committee 95
8.1 Introduction 96
8.2 Inquiry Format 96
8.3 Code Revisions or Additions 97
8.4 Code Interpretations 97
8.5 Submittals 97
Section 9 Glossary of Terms 99
9.1 Definitions 100
Section 10 NBIC Approved Interpretations 103
10.1 Scope 104
10.2 Index of Interpretations 104
10.3 Subject Index of Interpretations 108
Section 1 1 Index 1 1 1
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
piping, and other pressure-retaining items 1.4.2
shall not be operated until the required
documentation has been provided by the a)
installer to the owner and the Jurisdiction.
A07 b) The National Board Commissioned Inspec-
tor providing inservice inspection for the
facility in which the pressure-retaining item
is installed has the following responsibili-
ties:
A07 1 ) verify the Bo//er Installation Report (1-1
Report) has been completed and signed
by the installer, when required by the b)
Jurisidication;
A07 2) verify pressure-retaining items comply
with the laws and regulations of the
Jurisdiction governing the specific type
of boiler or pressure vessel;
A07 3) verify any repairs or alterations to
pressure-retaining items, which are
conducted prior to, or during, the initial 1.4.3
installation, are in accordance with the
NBIC; a)
A07 4) request or assign Jurisdictional identi-
fication number, when required by the
Jurisdiction; and
A07 5) complete and submit the first inservice
inspection/certificate report to the Juris-
diction when required by the Jurisdica- b)
tion.
A07 Unless otherwise specifically required by
the Jurisdiction, the duties of the inservice
inspector do not include the installation's
compliance to other standards and require-
ments (environmental, construction, elec-
trical, undefined industry standards, etc.)
for which other regulatory agencies have
authority and responsibility to oversee.
EQUIPMENT CERTIFICATION
All boilers, pressure vessels, piping, and
other pressure-retaining items shall have
documented certification from the manu-
facturer indicating that the boiler, pressure
vessel, piping, or any other pressure-retain-
ing items comply with the requirements of
the code of construction. The certification
shall identify the "Addenda" for a code of
construction to which all pressure-retaining A09
items were fabricated.
Package boilers having external piping
disassembled and shipped with the boiler
shall have a method for traceability of the
disassembled piping that can be verified
at the time of installation and inspection.
The manufacturer of the package boiler is
responsible for determining a method of
traceability.
JURISDICTIONAL REVIEW
The owner shall determine jurisdictional
requirements (i.e., certificates, permits,
licenses, etc.) before installing the equip-
ment. The organization responsible for
installation shall obtain all permits required
by the Jurisdiction prior to commencing
installation.
The owner shall determine jurisdictional
requirements (i.e., certificates, permits, li-
censes, etc.) before operating the equipment.
The owner shall obtain operating certificates,
permits, etc., required by the jurisdiction
prior to commencing operation.
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
1.4.4 INSPECTION
A07 All boilers, pressure vessels, piping, and other
pressure-retaining items shall be inspected and
tested after installation and prior to commenc-
ing operation.
1.4.5 BOILER INSTALLATION REPORT
a) Upon completion, inspection, testing and
acceptance of the installation, the installer
shall complete and certify the 6o/7er Instal-
lation Report (1-1) for all power boilers,
hot-water heating boilers, steam heating
boilers, hot-water supply boilers, and po-
table water heaters.
b) The Boiler Installation Report (1-1 ) shall be
submitted as follows:
1 ) One copy to the owner; and
2) One copy to the Jurisdiction, if
required.
1 D
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
is a guideline for estimating feed pump
differential:
Table 2.5.1.3
Guide for Feedpump Differential
Boiler Pressure
Boiler Feedwater
Pump Discharge
Pressure
psig
(MPa)
psig
(MPa)
200
(1.4)
250
(1.7)
400
(2.8)
475
(3.3)
800
(5.5)
925
(6.4)
1,200
(8.3)
1,350
(9.3)
b) For forced-flow steam generators with no
fixed steam or water line, each source
of feedwater shall be capable of supply-
ing feedwater to the boiler at a minimum
pressure equal to the expected maximum
sustained pressure at the boiler inlet cor-
responding to operation at maximum de-
signed steaming capacity with maximum
allowable pressure at the superheater
outlet.
c) Control devices may be installed on feed-
water piping to protect the pump against
overpressure.
2.5.1.4
VALVES
b)
The feedwater piping shall be provided with
a check valve and a stop valve. The stop
valve shall be located between the check
valve and the boiler.
When two or more boilers are fed from a
common source, there shall also be a globe
or regulating valve on the branch to each
boiler located between the check valve and
the feedwater source.
tions are equipped with stop and check
valves, the stop and check valve in the
common source may be omitted.
d) On single boiler-turbine unit installations,
the boiler feedwater stop valve may be lo-
cated upstream from the boiler feedwater
check valve.
e) If a boiler is equipped with duplicate
feedwater supply arrangements, each such
arrangement shall be equipped as required
by these rules.
f) A check valve shall not be a substitute for
a stop valve.
g) A combination feedwater stop-and-check
valve in which there is only one seat and
disk and a valve stem is provided to close
the valve when the stem is screwed down
shall be considered only as a stop valve, a
separate check valve shall be installed.
h) Whenever globe valves are used on feed-
water piping, the inlet shall be under the
disk of the valve.
i) Stop valves and check valves shall be
placed on the inlet of economizers or feed-
water-heating devices.
j) The recirculating return line for a high
temperature water boiler shall be provided
with the stop valve, or valves, required for
the main discharge outlet on the boiler.
2.5.2
FUEL
Fuel systems, whether firing coal, oil, gas, or
other substance, shall be installed in accor-
dance with jurisdictional and environmental re-
quirements, manufacturer's recommendations,
and/or industry standards, as applicable.
c) When the feedwater piping is divided into
branch connections and all such connec-
1 9
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
2.5.3
A09 2.6.3.1
ELECTRICAL
WIRING
All wiring for controls, heat generating appa-
ratus, and other appurtenances necessary for
the operation of the boiler or boilers should be
installed in accordance with the provisions of
national or international standards and comply
with the applicable local electrical codes.
shutdown switch(es) or circuit breaker(s)
must disconnect all power to the burner
controls.
f) For power burners with detached auxil- A09
iaries, the emergency remote shutdown
switch(es) or circuit breaker(s) need only
shut off the fuel input to the burner.
2.5.3.3 CONTROLS AND HEAT-
GENERATING APPARATUS
A09
A09 2.5.3.2 REMOTE EMERGENCY
SHUTDOWN SWITCHES
A09 a) A manually operated remote shutdown
switch or circuit breaker shall be located
just outside the boiler room door and
marked for easy identification. Consider-
ation should also be given to the type and
location of the switch to safeguard against
tampering.
A09 b) For boiler rooms exceeding 500 sq. ft.
(46.5 sq. m) floor area or containing one
or more boilers having a combined fuel
capacity of 1,000,000 Btu/hr (293kW) or
more, additional manually operated remote
emergency shutdown switches shall be lo-
cated at suitably identified points of egress
acceptable to the Jurisdiction.
A09 c) Where a boiler is located indoors in a
facility and not in a boiler room, a remote
emergency shutdown switch shall be lo-
cated within 50 feet of the boiler along the
primary egress route from the boiler area.
A09 d) Consideration should be given to the type
and location of the remote emergency
shutdown switch(es) to safeguard against
tampering. Where approved by the Ju-
risdiction, alternate locations of remote
emergency switch(es) may be provided.
A09 e ) For atmospheric-gas burners and for oil
burners where a fan is on the common shaft
with the oil pump, the emergency remote
a) Oil and gas-fired and electrically heated A09
boilers shall be equipped with suitable
primary (flame safeguard) safety controls,
safety limit switches and controls, and
burners or electric elements as required by
a nationally or internationally recognized
standard.
b) The symbol of the certifying organization A09
that has investigated such equipment as
having complied with a nationally rec-
ognized standard shall be affixed to the
equipment and shall be considered as
evidence that the unit was manufactured
in accordance with that standard.
c) These devices shall be installed in accor- A09
dance with jurisdictional and environmen-
tal requirements, manufacturer's recom-
mendations, and/or industry standards, as
applicable.
2.5.4 VENTILATION AND
COMBUSTION AIR
a) The boiler room shall have an adequate air
supply to permit clean, safe combustion,
minimize soot formation, and maintain
a minimum of 19.5% oxygen in the air
of the boiler room. The combustion and
ventilation air should be supplied by either
an unobstructed air opening or by power
ventilation or fans. 1
1 Fans - When combustion air is supplied to the boiler by
an independent duct, with or without the employment of power
ventilators or fans, the duct shall be sized and installed in ac-
cordance with the manufacturer's recommendations. However,
ventilation for the boiler room must still be considered.
2D
NATIONAL BOARD INSPECTION CODE * PART 1
INSTALLATION
b) Unobstructed air openings shall be sized 2.5.6
on the basis of 1 sq. in. (650 sq. mm) free
area per 2000 Btu/hr (586 W) maximum
fuel input of the combined burners located
in the boiler room, or as specified in the
National Fire Protection Association (NFPA)
standards for oil and gas burning installa-
tions for the particular job conditions. The
boiler room air supply openings shall be
kept clear at all times.
c) Power ventilators or fans shall be sized 2.6
on the basis of 0.2 cfm (0.0057 cu meters
per minute) for each 1000 Btu/hr (293 W)
of maximum fuel input for the combined 2.6.1
burners of all boilers located in the boiler
room. Additional capacity may be required
for any other fuel-burning equipment in the
boiler room.
d) When power ventilators or fans are used
to supply combustion air, they shall be
installed with interlock devices so that 2.6.2
the burners will not operate without an
adequate number of ventilators/fans in
operation.
e) The size of openings specified in 2.5.4(b)
may be reduced when special engineered
air supply systems approved by the Jurisdic-
tion are used. 2.6.3
EMERGENCY VALVES AND
CONTROLS
All emergency shut-off valves and controls shall
be accessible from a floor, platform, walkway,
or runway. Accessibility shall mean within a 6
ft. (1 .8 m) elevation of the standing space and
not more than 12 in. (305 mm) horizontally
from the standing space edge.
DISCHARGE REQUIREMENTS
CHIMNEY OR STACK
Chimneys or stacks shall be installed in accor-
dance with jurisdictional and environmental re-
quirements, manufacturer's recommendations,
and/or industry standards, as applicable.
ASH REMOVAL
Ash removal systems shall be installed in accor-
dance with jurisdictional and environmental re-
quirements, manufacturer's recommendations,
and/or industry standards, as applicable.
DRAINS
f) Care should be taken to ensure that steam
and water lines are not routed across com-
bustion air openings, where freezing may
occur in cold climates.
2.5.5
LIGHTING
The boiler room should be well lighted and it
should have an emergency light source for use
in case of power failure.
2.6.3.1 CONNECTION
a) Each boiler shall have at least one drain
pipe fitted with a stop valve at the lowest
point of the boiler. If the connection is not
intended for blowoff purposes, a single
valve is acceptable if it can be locked in
the closed position or a blank flange can
be installed downstream of the valve. If
the connection is intended for blowoff
purposes, requirements of 2.7.5 shall be
followed.
b) For high temperature water boilers, the
minimum size of the drain pipe shall be
NPS1 (DN25).
2 1
NATIONAL BOARD INSPECTION CODE • PART 1
INSTALLATION
c) Drain pipes, valves, and fittings within the
same drain line shall be the same size.
d) The discharge from the drain shall be piped
to a safe location.
2.6.3.2 PRESSURE RATING
a) When the maximum allowable working
pressure of the boiler is equal to or less
than 101 .5 psig (700 kPa), the drain pipe,
valve, and fittings shall be rated for at least
A07 1 00 psig (700 kPa) and 220°F (1 04°C).
b) When the maximum allowable working
pressure of the boiler exceeds 1 00 psig (700
kPa), the drain pipe, valve, and fittings shall
be rated for at least the maximum allowable
working pressure and temperature of the
boiler.
2.6.3.3
PARTS
a) When parts (economizers, etc.) are installed
with a stop valve between the part and the
boiler or the part cannot be completely
drained through the drain on the boiler, a
separate drain shall be installed on each
such part. These drains shall meet the addi-
tional requirements of 6.3, as applicable.
b) Each water column shall have a drain pipe
fitted with a stop valve at the lowest point of
the water column. The stop valve shall have
the capability of being locked in the closed
position while the boiler is under pressure.
The minimum size of the drain shall beNPS
3/4 (DN 20) and all other requirements of
6.3, as applicable.
2.7 OPERATING SYSTEMS
2.7.1
BREECHING AND DAMPERS
Breeching and dampers shall be installed in
accordance with jurisdictional and environ-
mental requirements, manufacturer's recom-
mendations, and/or industry standards, as
applicable.
2.7.2
BURNERS AND STOKERS
Burners and stokers shall be installed in accor-
dance with jurisdictional and environmental re-
quirements, manufacturer's recommendations,
and/or industry standards, as applicable.
2.7.3
STEAM SUPPLY
a) Provisions shall be made for the expansion
and contraction of steam mains connected
to boiler(s) so that there shall be no undue
stress transmitted to the boiler(s). Steam
reservoirs shall be installed on steam mains
when heavy pulsations of the steam flow
causes vibration of the boiler shell plates.
b) Each discharge outlet of the boiler drum or
superheater outlet shall be fitted with a stop
valve located at an accessible point in the
steam-delivery line and as near the boiler
nozzle as is convenient and practicable.
The valve shall be equipped to indicate
from a distance whether it is closed or open,
and shall be equipped with a slow-opening
mechanism. When such outlets are over
NPS 2 (DN 50), the valve or valves used
on the connection shall be of the outside
screw-and-yoke-rising spindle type, so as
to indicate from a distance by the position
of its spindle whether it is closed or open
and the wheel should be carried either on
the yoke or attached to the spindle. In the
case of a single boiler and prime mover
installation, the stop valve may be omitted
provided the prime mover throttle valve
is equipped with an indicator to show
whether the valve is open or closed and is
designed to withstand the required hydro-
static test pressure of the boiler.
c) Stop valves and fittings shall comply with
the appropriate national standard except
that austenitic stainless steel is not permit-
ted for water wetted service.
22
NATIONAL BOARD INSPECTION CODE • PART 1
INSTALLATION
a)
d) Stop valves and fittings shall be rated for 2.7.4
the maximum allowable working pressure
of the boiler and shall be at least rated for
1 00 psig (700 kPa) at the expected steam
temperature at the valve or fitting, in ac-
cordance with the appropriate national
standard.
e) The nearest stop valve or valves to the su-
perheater outlet shall have a pressure rating
at least equal to the minimum set pressure
of any safety valve on the superheater 2.7.5
and at the expected superheated steam
temperature; or at least equal to 85% of
the lowest set pressure of any safety valve
on the boiler drum at the expected steam
temperature of the superheater outlet,
whichever is greater.
f) Ample provision for gravity drain shall be
provided when a stop valve is so located
that water or condensation may accumu-
late. The gravity drain(s) shall be located
such that the entire steam supply system
can be drained.
g) When boilers are connected to a common
header, the connection from each boiler
having a manhole opening shall be fitted
with two stop valves having an ample free-
blow drain between them. The discharge of
this drain shall be visible to the operator
while operating the valve. The stop valves
shall consist of one stop check valve (set
next to the boi ler) and a second valve of the
outside screw-and-yoke type; or two valves
of the outside screw-and-yoke type.
CONDENSATE AND RETURN
Each condensate return pump where practi-
cable, shall be provided with an automatic
water level control set to maintain an adequate
water level in the condensate tank. Condensate
tanks not constructed in accordance with an
accepted code or standard shall be vented to
the atmosphere.
h) The second steam stop valve shall have
a pressure rating at least equal to that re-
quired for the expected steam temperature
and pressure at the valve; or the pressure
rating shall be not less than 85% of the low-
est set pressure of any safety valve on the
boiler drum and for the expected tempera-
ture of the steam at the valve, whichever is
greater. f)
i) Pressure-reducing valves may be installed
in the steam supply piping downstream
from the required stop valve or valves.
BLOWOFF
Except for forced-flow steam generators
with no fixed steam or water line, each
boiler shall have a blowoff pipe, fitted with
a stop valve, in direct connection with the
lowest water space practicable. When the
maximum allowable working pressure of
the boiler exceeds 1 00 psig (700 kPa), there
shall be two valves installed.
b) The blowoff piping for each electric boiler
pressure vessel having a nominal water
content not exceeding 100 gal. (378 I) is re-
quired to extend through only one valve.
c) When two valves are required, each bottom
blowoff pipe shall have two slow-opening
valves, or one quick-opening valve, at the
boiler nozzle followed by a slow-opening
valve.
d) Two independent slow-opening valves or
a slow-opening valve and quick-opening
valve may be combined in one body pro- A09
vided the combined fitting is the equivalent
of two independent slow-opening valves or
a slow-opening valve and a quick-opening
valve, and the failure of one to operate can-
not affect the operation of the other.
e) Straight-run globe valves or valves where
dams or pockets can exist for the collection A08
of sediment shall not be used.
The blowoff valve or valves and the pipe and
fittings between them and the boiler shall be
of the same size. The minimum size of pipe
and fittings shall be NPS 1 (DN 25), except
boilers with 1 00 sq. ft (9.3 sq. m) of heating
23
NATIONAL BOARD INSPECTION CODE • PART 1
INSTALLATION
surface or less should be NPS 3/4 (DN 20).
The maximum size of pipe and fittings shall
not exceed NPS 2-1/2 (DN 65).
g) For electric boilers, the minimum size of
blowoff pipes and fittings shall be NPS 1
(DN 25), except for boilers of 200 kW input
or less. The minimum size should be NPS
3/4 (DN 20).
h) Fittings and valves shall comply with the
appropriate national standard except that
austenitic stainless steel and malleable iron
are not permitted.
i) When the maximum allowable working
pressure exceeds 1 00 psig (700 kPa), blow-
off piping shall be at least Schedule 80 and
the required valves and fittings shall be
rated for at least 1 .25 times the maximum
allowable working pressure of the boiler.
When the maximum allowable working
pressure exceeds 900 psig (6.2 MPa), blow-
off piping shall be at least Schedule 80 and
the required valves and fittings shall be
rated for at least the maximum allowable
working pressure of the boiler plus 225 psi
(1.6 MPa).
j) All blowoff piping, when exposed to fur-
nace heat, shall be protected by fire brick or
other heat resisting material so constructed
that the piping may be readily inspected.
k) On a boiler having multiple blowoff pipes,
a single master stop valve should be placed
on the common blowoff pipe from the
boiler and one stop valve on each indi-
vidual blowoff. Either the master valve or
the valves on the individual blowoff lines
shall be of the slow-opening type.
I) The discharge of blowoff pipes shall be lo-
cated so as to prevent injury to personnel.
m) All waterwalls or water screens that do
not drain back into the boiler and integral
economizers forming part of a boiler shall
be equipped with blowoff piping and valves
conforming to the requirements of this
paragraph.
n) Blowoff piping from a boiler should not
discharge directly into a sewer. A blowoff
tank, constructed to the provisions of a
code of construction acceptable to the Ju-
risdiction, shall be used where conditions
do not provide an adequate and safe open
discharge.
o) Galvanized pipe shall not be used.
p) Boiler blowoff systems shall be constructed
in accordance with the Guide for Blowoff
Vesse/s(NB-27). 2
q) Where necessary to install a blowoff tank
underground, it shall be enclosed in a con-
crete or brick pit with a removable cover so
that inspection of the entire shell and heads
of the tank can be made.
r) Piping connections used primarily for con-
tinuous operation, such as deconcentrators
on continuous blowdown systems, are not
classed as blowoffs; but the pipe connec-
tions and all fittings up to and including
the first shutoff valve shall be equal at least
to the pressure requirements for the low-
est set pressure of any safety valve on the
boiler drum and with the corresponding
saturated-steam temperature. Further, such
connections shall not exceed NPS 2-1/2
(DN 65).
2.8 CONTROLS AND GAGES
2.8.1
WATER
b)
Each automatically fired steam boiler shall
be equipped with at least two low-water fuel
cutoffs. The water inlet shall not feed water
into the boiler through a float chamber.
Each electric steam boiler of the resistance
element type shall be equipped with an
automatic low-water cutoff so located as
to automatically cut off the power supply
2 The Guide for Blowoff Vessels(NB-27) can be found on the
National Board Web site, www.nationaiboard.org, under the E-
Publications/Directories menu button.
24
NATIDNAL BOARD INSPECTION CODE • PART 1
INSTALLATION
to the heating elements before the surface
of the water falls below the visible part of
the glass. No low-water cutoff is required
for electrode-type boilers.
c) Designs embodying a float and float bowl
shali have a vertical straightaway drainpipe
at the lowest point in the water equalizing
pipe connections, by which the bowl and
the equalizing pipe can be flushed and the
device tested.
d) The water column shall be directly connect-
ed to the boiler. Outlet connections (except
for damper regulator, feedwater regulator,
low-water fuel cutoff, drains, steam gages,
or such apparatus that does not permit the
escape of an appreciable amount of steam
or water) should not be placed on the pip-
ing that connects the water column to the
boiler.
e) Straight-run globe valves of the ordinary
type shall not be used on piping that con-
nects the water column to the boiler. Where
water columns are 7 ft. (2.1 m) or more
above the floor level, adequate means for
operating gage cocks or blowing out the
water glass shall be provided.
f) When automatic shutoff valves are used
on piping that connects the water column
to the boiler, they shall conform to the re-
quirements of the code of construction for
the boiler.
g) When shutoff valves are used on the con-
nections to a water column, they shall be
either outside-screw-and-yoke or lever-
lifting-type gate valves or stop cocks with
levers permanently fastened thereto and
marked in line with their passage, or of such
other through-flow constructions to prevent
stoppage by deposits of sediment and to
indicate by the position of the operating
mechanism whether they are in open or
closed position; and such valves or cocks
shall be locked or sealed open.
h) Each steam boiler having a fixed waterline
shall have at least one water-gage glass
except that boilers operated at pressures
over 400 psig (2.8 MPa) shall be provided
with two water-gage glasses that may be
connected to a single water column or con-
nected directly to the drum. The gage glass
connections and pipe connection shall be
not less than NPS 1/2 (DN 1 5). Each water-
gage glass shall be equipped with a valved
drain.
i) Electric steam boilers shall have at least one
water-gage glass. On electrode-type electric
boilers, the gage glass shall be located as
to indicate the water levels both at startup
and maximum steam load conditions, as
established by the boiler manufacturer.
On resistance element type electric steam
boilers, the lowest visible part of the gage
glass shall be located at least 1 in. (25 mm)
above the lowest permissible water level
established by the boiler manufacturer.
j) The lowest visible part of the water-gage
glass shall be at least 2 in. (50 mm) above
the lowest permissible water level estab-
lished by the boiler manufacturer.
k) For all installations where the water-gage
glass or glasses are not easily viewed by the
operator, consideration should be given to
install a method of remote transmission of
the water level to the operating floor.
I) Boilers of the horizontal firetube type shall
be so set that when the water is at the lowest
reading in the water gage glass, there shall
be at least 3 in. (75 mm) of water over the
highest point of the tubes, flues, or crown
sheet.
m) Each water-gage glass shall be equipped
with a top and a bottom shutoff valve of
such through-flow construction as to pre-
vent blockage by deposits of sediment and
to indicate by the position of the operating
mechanism whether they are in the open
or closed position. The pressure-tempera-
ture rating shall be at least equal to that of
the lowest set pressure of any safety valve
on the boiler drum and the corresponding
saturated steam temperature.
25
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
A07 2.8.2
PRESSURE GAGE
2.9
PRESSURE RELIEF VALVES
a) Each steam boiler shall have a pressure
gage connected to the steam space or to
the steam connection to the water column.
When a pressure-reducing valve is installed
in the steam supply piping, a pressure gage
shall be installed on the low pressure side
of the pressure-reducing valve.
b) The dial range shall not be less than 1.5
times or no greater than two times the
A09 pressure at which the lowest pressue-relief
valve is set.
A07
2.8.2.1
CONNECTION
a) For a steam boiler the gage or connection
shall contain a siphon or equivalent device
that will develop and maintain a water seal
that will prevent steam from entering the
gage tube. A valve or cock shall be placed
in the gage connection adjacent to the
gage. An additional valve or cock should be
located near the boiler providing it is locked
or sealed in the open position. No other
shut-off valves shall be located between
the gage and the boiler.
b) Pressure gage connections shall be suitable
for the maximum allowable working pres-
sure and temperature, but if the temperature
exceeds 406°F (208°C), brass or copper
pipe or tubing shall not be used. The con-
nections to the boiler, except for the siphon,
if used, shall not be less than NFS 1/4 (DN
8). Where steel or wrought iron pipe or
tubing is used, it shall not be less than 1/2
in. (1 3 mm) inside diameter. The minimum
size of a siphon, if used, shall be 1/4 in. (6
mm) inside diameter.
2.9.1 VALVE REQUIREMENTS —
GENERAL
a) Safety valves are designed to relieve steam.
b) Safety relief valves are valves designed to
relieve either steam or water, depending on
the application.
c) Safety and safety relief valves are to be
manufactured in accordance with a na-
tional or international standard.
d) Deadweight or weighted-lever pressure-
relieving valves shall not be used.
e) For high temperature water boilers, safety
relief valves shall have a closed bonnet,
and safety relief valve bodies shall not be
constructed of cast iron.
f) Safety and safety relief valves with an inlet
connection greater than NPS 3 (DN 80)
used for pressure greater than 1 5 psig (1 03
kPa), shall have a flange inlet connection
or a welding-end inlet connection. The
dimensions of flanges subjected to boiler
pressure shall conform to the applicable
standards.
g) When a safety or safety rel ief valve is exposed
to outdoor elements that may affect operation
of the valve, it is permissible to shield the
valve with acover. The cover shall be properly
vented and arranged to permit servicing and
normal operation of the valve.
2.9.1.1
NUMBER
2.8.3
TEMPERATURE
Each high temperature water boiler shall have
a temperature gage or other reporting device
located to provide an accurate representation of
the temperature at or near the boiler outlet.
At least one National Board capacity certified
safety or safety relief valve shall be installed on
the boiler. If the boiler has more than 500 sq. ft.
(46 sq. m.) of heating surface, or if an electric
boiler has a power input of more than 3.76 mil-
lion BTU/hr (1 1 00 kW), two or more National
Board capacity certified safety or safety relief
valves shall be installed.
A07
zs
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
^m * Jf * I 4^1
LOCATION
a) Safety or safety relief valves shall be placed
on, or as close as physically possible, to the
boiler proper.
b) Safety or safety relief valves shall not be
placed on the feedline.
c) Safety or safety relief valves shall be con-
nected to the boiler independent of any
other connection without any unnecessary
intervening pipe or fittings. Such interven-
ing pipe or fittings shall not be longer than
the face-to-face dimension of the corre-
sponding tee fitting of the same diameter
and pressure rating as listed in the appli-
cable standards.
2.9.1.3 CAPACITY
a) The pressure-relieving valve capacity for
each boiler shall be such that the valve or
valves will discharge all the steam that can
be generated by the boiler without allowing
the pressure to rise more than 6% above
the highest pressure at which any valve is
set and in no case to more than 6% above
the maximum allowable working pressure
of the boiler.
b) The minimum relieving capacity for other
than electric boilers and forced-flow steam
generators with no fixed steam line and
waterline shall be estimated for the boiler
and waterwall heating surfaces as given in
Table 2.9.1.3, but in no case should the
minimum relieving capacity be less than
the maximum designed steaming capacity
as determined by the manufacturer.
c) The required relieving capacity in pounds
per hour of the safety or safety relief valves
on a high temperature water boiler shall
be determined by dividing the maximum
output in Btu at the boiler nozzle obtained
by the firing of any fuel for which the unit
is designed by one thousand.
d) The minimum safety or safety relief valve
relieving capacity for electric boilers is 3.5
Ibs/hr/kW (1 .6 kg/hr/kW) input.
e) If the safety or safety relief valve capacity
cannot be computed, or if it is desirable
to prove the computations, it should be
checked by any one of the following meth-
ods; and if found insufficient, additional
relieving capacity shall be provided:
1) By performing an accumulation test,
that is, by shutting off all other steam
discharge outlets from the boiler and
forcing the fires to the maximum. This
method should not be used on a boiler
with a superheater or reheater or on a
high temperature water boiler.
2) By measuring the maximum amount of
fuel that can be burned and computing
the corresponding evaporative capacity
upon the basis of the heating value of
the fuel.
3) By determining the maximum evapo-
rative capacity by measuring the feed-
water. The sum of the safety valve ca-
pacities marked on the valves shall be
equal to or greater than the maximum
evaporative capacity of the boiler. This
method should not be used on high
temperature water boilers.
27
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
Table 2.9.1.3 - Minimum Pounds of steam
per hour per square foot of
Heating Surface 1 lb steam/hr/sq.ft (kg/hr/
sq m)
A08
Firetube Boilers
Boiler heating surface
Watertube Boilers
A08
A08
A08
A07
A08
A08
A08
hand-fired
stoker-fired
oil, gas, or pulverized fuel-fired
5(24)
7(34)
(39)
Waterwall heating surface
hand-fired
stoker-fired
oil, gas, or pulverized fuel-fired
(39)
1 (49)
14
Copper-finned watertubes
hand-fired
stoker-fired
oil, gas, or pulverized fuel-fired
6(29)
(39)
10(49)
(39)
12 (59)
16(78)
4(20)
5(24)
6(29)
NOTES:
• When a boiler is fired only by a gas having a heat value not in excess of 200 Btu/cu.ft.(7.5MJ/cu. m), the mini-
mum relieving capacity should be based on the values given for hand-fired boilers above.
• The heating surface shall be computed for that side of the boiler surface exposed to the products of combustion,
exclusive of the superheating surface. In computing the heating surface for this purpose only the tubes, fireboxes,'
shells, tubesheets, and the projected area of headers need to be considered, except that for vertical firetube steam
boilers, only that portion of the tube surface up to the middle gage cock is to be computed.
• For firetube boiler units exceeding 8000 Btu/ft. 2 (9085 J/cm. 2 ) (total fuel Btu (J) Input divided by total heating
surface), the factor from the table will be increased by 1 (4.88) for every 1000 Btu/ft. 2 (1136J/cm. 2 ) above
8000 Btu/ft. 2 (9085 J/cm. 2 ) For units less than 7000 Btu/ft. 2 (7950 J/cm. 2 ), the factor from the table will be
decreased by 1 (7950 J/cm. 2 ).
• For watertube boiler units exceeding 1 6000 Btu/ft. 2 (1 81 70 J/cm. 2 )(total fuel BTU input divided by the total
heating surface) the factor from the table will be increased by 1 (4.88) for every 1 000 Btu/ft. 2 (1136 J/cm. 2 )
above 1 6000 Btu/ft. 2 (1 81 70 J/cm. 2 ). For units with less than 1 5000 Btu/ft. 2 (1 7034 J/cm. 2 ), the factor in the
table will be decreased by 1 (4.88) for every 1 000 Btu/ft. 2 (1136 J/cm. 2 ) below 1 5000 Btu/ft. 2 (1 7034 J/cm. 2 ).
2B
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
2.9.1.4 SET PRESSURE
One or more safety or safety relief valves on
the boiler proper shall be set at or below the
maximum allowable working pressure. If ad-
ditional valves are used, the highest pressure
setting shall not exceed the maximum allow-
able working pressure by more than 3%. The
complete range of pressure settings of all the
safety relief valves on a boiler shall not exceed
10% of the highest pressure to which any valve
is set. Pressure setting of safety relief valves on
high temperature water boilers may exceed
this 10% range.
2.9.2 FORCED-FLOW STEAM
GENERATOR
For a forced-flow steam generator with no
fixed steamline and waterline, equipped with
automatic controls and protective interlocks
responsive to steam pressure, safety valves
A08 may be provided in accordance with the above
paragraphs identified in 2.9.1 or the follow-
ing protection against overpressure shall be
provided:
a) One or more power-actuated pressure-re-
lieving valves shall be provided in direct
communication with the boiler when the
boiler is under pressure and shall receive
a control impulse to open when the maxi-
mum allowable working pressure at the
superheater outlet is exceeded. The total
combined relieving capacity of the power-
actuated pressure-relieving valves shall be
not less than 10% of the maximum design
steaming capacity of the boiler under any
operating condition as determined by the
manufacturer. The valves shall be located
in the pressure part system where they will
relieve the overpressure. An isolating stop
valve of the outside-screw-and-yoke type
should be installed between the power-
actuating pressure-relieving valve and
the boiler to permit repairs provided an
alternate power-actuated pressure-relieving
valve of the same capacity is so installed
as to be in direct communication with the
boiler.
b) Spring-loaded safety valves shall be pro-
vided having a total combined relieving ca-
pacity, including that of the power-actuated
pressure-relieving valve, of not less than
1 00% of the maximum designed steaming
capacity of the boiler, as determined by the
manufacturer. In this total, credit in excess
of 30% of the total relieving capacity shall A07
not be allowed for the power-actuated
pressure-relieving valves actually installed.
Any or all of the spring-loaded safety valves
may be set above the maximum allowable
working pressure of the parts to which they
are connected, but the set pressures shall
be such that when all these valves (together
with the power-actuated pressure-relieving
valves) are in operation the pressure will not
rise more than 20% above the maximum
allowable working pressure of any part
of the boiler, except for the steam piping
between the boiler and the prime mover.
c) When stop valves are installed in the water-
steam flow path between any two sections
of a forced-flow steam generator with no
fixed steamline and waterline:
1) The power-actuated pressure-reliev-
ing valve shall also receive a control
impulse to open when the maximum
allowable working pressure of the
component, having the lowest pres-
sure level upstream to the stop valve,
is exceeded.
2) The spring-loaded safety valve shall
be located to provide overpressure
protection for the component having
the lowest working pressure.
3) A reliable pressure-recording device
shall always be in service and records
kept to provide evidence of conformity
to the above requirements.
29
NATIDNAL BOARD INSPECTION CODE • PART 1
INSTALLATION
2.9.3
SUPERHEATERS
a) Every attached superheater shall have one
or more safety valves. The location shall
be suitable for the service intended and
shall provide the overpressure protection
required. The pressure drop upstream of
each safety valve shall be considered in
determining the set pressure and relieving
capacity of that valve. If the superheater
outlet header has a full, free steam passage
from end to end and is so constructed that
steam is supplied to it at practically equal
intervals throughout its length so that there
is a uniform flow of steam through the su-
perheater tubes and the header, the safety
valve or valves may be located anywhere
in the length of header.
b) The pressure-relieving capacity of the safety
valve or valves on an attached superheater
shall be included in determining the num-
ber and size of the safety valves for the
boiler provided there are no intervening
valves between the superheater safety valve
and the boiler and the discharge capacity
A07 of the safety relief valve or valves, on the
boiler, as distinct from the superheater,
is at least 75% of the aggregate capacity
required.
c) Every independently fired superheater that
may be shut off from the boiler and permit
the superheater to become a fired pressure
vessel shall have one or more safety valves
having a discharge capacity equal to six
pounds of steam per hr/sq. ft. (29 kg per hr
per sq. m) of superheater surface measured
on the side exposed to the hot gases.
d) Every safety valve used on a superheater
discharging superheated steam at a tem-
perature over 450°F (230°C) shall have a
casing, including the base, body, bonnet,
and spindle constructed of steel, steel alloy,
or equivalent heat-resistant material. The
valve shall have a flanged inlet connection
or a welding-end inlet connection. The seat
and disk shall be constructed of suitable
heat-erosive and corrosive-resistant mate-
rial, and the spring fully exposed outside of
the valve casing so that it is protected from
contact with the escaping steam.
2.9.4
ECONOMIZERS
An economizer that may not be isolated from
a boiler does not require a safety relief valve.
Economizers that may be isolated from a boiler
or other heat transfer device, allowing the
economizer to become a fired pressure vessel,
shall have a minimum of one safety relief valve.
Discharge capacity, rated in Ibs/hr (kg/hr), of the
safety relief valve or valves shall be calculated
from the maximum expected heat absorption
rate in Btu/hr (Joules/hr) of the economizer, and
will be determined from manufacturer data,
divided by 1000. The safety relief valve shall
be located as close as possible to the econo-
mizer outlet.
2.9.5 PRESSURE-REDUCING VALVES
a) Where pressure-reducing valves are used,
one or more safety or safety relief valves
shall be installed on the low pressure side
of the reducing valve in those installations
where the piping or equipment on the low
pressure side does not meet the require-
ments for the steam supply piping.
b) The safety or safety relief valves shall be
located as close as possible to the pressure-
reducing valve.
c) Capacity of the safety or safety relief valves
shall not be less than the total amount of
steam that can pass from the high pres-
sure side to the low pressure side and be
such that the pressure rating of the lower
pressure piping or equipment shall not be
exceeded.
d) The use of hand-controlled bypasses around
reducing valves is permissible. The bypass
around a reducing valve may not be greater
in capacity than the reducing valve unless the
piping or equipment is adequately protected
by safety or safety relief valves or meets the
requirements of the high pressure system.
3D
NATIONAL BOARD INSPECTION CODE • PART 1
INSTALLATION
A09 2.9.6 MOUNTING AND DISCHARGE
REQUIREMENTS
a) Every boiler shall have outlet connections
for the safety or safety relief valve, or valves,
independent of any other outside steam
connection, the area of opening shall be at
least equal to the aggregate areas of inlet
connections of all of the attached safety
or safety relief valves. An internal collect-
ing pipe, splash plate, or pan should be
used, provided the total area for inlet of
steam thereto is not less than twice the
aggregate areas of the inlet connections of
the attached safety or safety relief valves.
The holes in such collecting pipes shall
be at least 1/4 in. (6 mm) in diameter, and
the least dimension in any other form of
opening for inlet of steam shall be 1/4 in.
(6 mm). If safety or safety relief valves are
attached to a separate steam drum or dome,
the opening between the boiler proper and
the steam drum or dome shall be not less
than 10 times the total area of the safety
valve inlet.
b) Every safety or safety relief valve shall be
connected so as to stand in an upright posi-
tion with spindle vertical.
c) The opening or connection between the
boiler and the safety or safety relief valve
shall have at least the area of the valve
inlet. No valve of any description should
be placed between the safety or safety
relief valves and the boiler, nor on the dis-
charge pipe between the safety or safety
relief valves and the atmosphere. When a
discharge pipe is used, the cross-sectional
area shall not be less than the full area of
the valve outlet or of the total of the areas
of the valve outlets, discharging thereinto
and shall be as short and straight as pos-
sible and arranged to avoid undue stresses
on the valve or valves.
d) When two or more safety valves are used
on a boiler, they should be mounted either
separately or as twin valves made by plac-
ing individual valves on Y-bases, or duplex
valves having two valves in the same body
casing. Twin valves made by placing indi-
vidual valves on Y-bases or duplex valves
having two valves in the same body shall
be of equal size.
e) When two valves of different sizes are
mounted singly, the relieving capacity of
the smaller valve shall not be less than 50%
of that of the larger valve.
f) When a boiler is fitted with two or more
safety relief valves on one connection, this
connection to the boiler shall have a cross-
sectional area not less than the combined
areas of inlet connections of all the safety
relief valves with which it connects.
g) All safety or safety relief valves shall be
piped to a safe point of discharge so located
or piped as to be carried clear from running
boards or platforms. Ample provision for
gravity drain shall be made in the discharge
pipe at or near each safety or safety relief
valve, and where water or condensation
may collect. Each valve shall have an open
gravity drain through the casing below the
level of the valve seat. For iron- and steel-
bodied valves exceeding NPS 2 (DN 50),
the drain hole shall be tapped not less than
NPS 3/8 (DN 10).
h) Discharge piping from safety relief valves
on high temperature water boilers shall
have adequate provisions for water drain-
age as well as steam venting.
i) If a muffler is used on a safety or safety relief
valve, it shall have sufficient outlet area
to prevent back pressure from interfering
with the proper operation and discharge
capacity of the valve. The muffler plates or
other devices shall be so constructed as to
avoid a possibility of restriction of the steam
passages due to deposits. Mufflers shall not
be used on high temperature water boiler
safety relief valves.
3 1
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
2.10 TESTING AND ACCEPTANCE
2.10.1 GENERAL
shipped connected to the boiler as a unit, shall
be hydrostatically tested with the boiler and
witnessed by an Inspector.
a) Care shall be exercised during installation
to prevent loose weld material, welding
rods, small tools, and miscellaneous scrap
metal from getting into the boiler. Where
possible, an inspection of the interior of the
boiler and its appurtenances shall be made
for the presence of foreign debris prior to
making the final closure.
A07 b) Safe operation should be verified by a per-
son familiar with boiler system operations
for all boilers and connected appurtenances
and all pressure piping connecting them to
the appurtenances and all piping up to and
including the first stop valve, or the second
stop valve when two are required.
c) The wall thickness of all pipe connections
shall comply with the requirements of the
code of construction for the boiler.
d) All threaded pipe connections shall engage
at least five full threads of the pipe or fit-
ting.
e) In bolted connections, the bolts, studs, and
nuts shall be marked as required by the
original Code of Construction and be fully
engaged (e.g., the end of the bolt or stud
shall protrude through the nut).
f) Washers shall only be used when speci-
fied by the manufacturer of the part being
installed.
2.10.2
PRESSURE TEST
Prior to initial operation, the completed boiler,
including pressure piping, water columns,
superheaters, economizers, stop valves, etc.,
shall be pressure tested in accordance with
the original code of construction. Any pres-
sure piping and fittings such as water columns,
blowoff valves, feedwater regulators, superheat-
ers, economizers, stop valves, etc., which are
2.10.3 NONDESTRUCTIVE
EXAMINATION
Boiler components and subcomponents shall
be nondestructively examined as required by
the governing Code of Construction.
2.10.4 SYSTEM TESTING
Prior to final acceptance, an operational test
shall be performed on the complete installation.
The test data shall be recorded and the data
made available to the jurisdictional authori-
ties as evidence that the installation complies
with the provisions of the governing code(s) of
construction. This operational test may be used
as the final acceptance of the unit.
2.10.5
FINAL ACCEPTANCE
A boiler may not be placed into service until its
installation has been inspected and accepted by
the appropriate jurisdictional authorities.
2.10.6 BOILER INSTALLATION REPORT
a) Upon completion, inspection, and accep-
tance of the installation, the installer shall
complete and certify the Boiler Installation
Report 1-1. See 1.4.5.1.
b) The Boiler Installation Report 1-1 shall be
submitted as follows:
1 ) one copy to the Owner; and
2) one copy to the Jurisdiction, if re-
quired.
32
NATIDNAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
3.3.4
CLEARANCES
3.4.2
LADDERS AND RUNWAYS
a) Heating boilers shall have a minimum
distance of at least 36 in. (914 mm) be-
tween the top of the heating boiler and
any overhead structure and at least 36 in.
(914 mm) between all sides of the heating
boiler and adjacent walls, structures, or
other equipment. Heating boilers having
A07 manholes shall have at least 84 in. (2135
mm) of clearance between the manhole
opening and any wall, ceiling, piping,
or other equipment that may prevent a
person from entering the heating boiler.
Alternative clearances in accordance with
the manufacturer's recommendations are
subject to acceptance by the Jurisdiction.
b) Modular heating boilers that require indi-
vidual units to be set side by side, front to
back or by stacking shall provide clearances
in accordance with the manufacturer's
recommendations, subject to acceptance
by the Jurisdiction.
c) Heating boilers shall be located so that
adequate space is provided for proper op-
eration, maintenance, 3 and inspection of
equipment and appurtenances.
a) All walkways, runways, and platforms shall
be:
1 ) of metal construction;
2) provided between or over the top of
boilers that are more than 8 ft. (2.4 m)
above the operating floor to afford ac-
cessibility for normal operation, main- A07
tenance, and inspection;
3) constructed of safety treads, standard
grating, or similar material and have a
minimum width of 30 in. (760 mm);
4) of bolted, welded, or riveted construc-
tion; and
5) equipped with handrails 42 in. (1070
mm) high with an intermediate rail and
4 in. (1 00 mm) toe board.
b) Stairways that serve as a means of access
to walkways, runways, or platforms shall
not exceed an angle of 45 degrees from the
horizontal and be equipped with handrails
42 in. (1 070 mm) high with an intermediate
rail. A09
3.4
3.4.1
BOILER ROOM REQUIREMENTS
EXIT
Two means of exit shall be provided for boiler
rooms exceeding 500 sq. ft. (46.5 sq. m) of floor
area and containing one or more boilers having
a combined fuel capacity of 1 ,000,000 Btu/hr
(293 kW) or more (or equivalent electrical heat
input). Each elevation shall be provided with
A07 at least two means of exit, each to be remotely
located from the other. A platform at the top of
a single boiler is not considered an elevation.
Maintenance -This includes the removal of tubes.
c) Ladders that serve as a means of access to
walkways, runways, or platforms shall:
1 ) be of metal construction and not less
than 18 in. (460 mm) wide;
2) have rungs that extend through the
side members and are permanently
secured;
3) have a clearance of not less than 30
in. (760 mm) from the front of rungs to
the nearest permanent object on the
climbing side of the ladder;
4) have a clearance of not less than 6-1 12
in. (1 65 mm) from the back of rungs to
the nearest permanent object; and
37
NATIONAL BOARD INSPECTION CODE • PART 1
INSTALLATION
5) have a clearance width of at least 1 5 in.
(380 mm) from the center of the ladder
on either side across the front of the
ladder.
d) There shall be at least two permanently
A07 installed means of exit from walkways,
runways, or platforms that exceed 6 ft. (1 .8
m) in length.
3.5
3.5.1
SOURCE REQUIREMENTS
WATER
a) A means to add water to or fill the boiler,
while not under pressure, shall be provided.
A valve or threaded plug may be used to
shut off the fill connection when the boiler
is in service.
A08 b) Water fill connections shall be installed.
A means shall be provided at or near the
boiler to prevent backfeeding. Such means
shall be rated for the boiler design pressure
and temperature.
c) Provision should also be made in every
boiler room for a convenient water supply
that can be used to flush out the boiler and
to clean the boiler room floor.
3.5.2
FUEL
Fuel systems, whether firing coal, oil, gas, or
other substance, shall be installed in accor-
dance with jurisdictional and environmental re-
quirements, manufacturer's recommendations,
and/or industry standards, as applicable.
3.5.3
ELECTRICAL
a) All wiring for controls, heat generating ap-
paratus, and other appurtenances necessary
for the operation of the boiler or boilers
shall be installed in accordance with the
provisions of national or international
standards and comply with the applicable
local electrical codes.
b) A manually operated remote shutdown
switch or circuit breaker shall be located A07
just outside the boiler room door and
marked for easy identification. Consider-
ation should also be given to the type and
location of the switch to safeguard against
tampering.
c) If the boiler room door is on the building
exterior, the switch shall be located just
inside the door. If there is more than one
door to the boiler room, there shall be a
switch located at each door of egress. A07
1) For atmospheric-gas burners, and oil
burners where a fan is on a common
shaft with the oil pump, the complete
burner and controls should be shut
off.
2) For power burners with detached auxil-
iaries, only the fuel input supply to the
firebox need be shut off.
d) Controls and Heat Generating Apparatus
1) Oil- and gas-fired and electrically
heated boilers and water heaters shall
be equipped with suitable primary
(flame safeguard) safety controls, safety
limit switches, and burners or electric
elements as required by a nationally or
internationally recognized standard.
2) The symbol of the certifying orga-
nization that has investigated such
equipment as having complied with a
nationally recognized standard shall
be affixed to the equipment and shall
be considered as evidence that the unit
was manufactured in accordance with
that standard.
38
NATIONAL BOARD INSPECTION CODE • PART 1
INSTALLATION
c) Potable Water Heaters
1) Water supply shall be introduced into
a water heater through an independent
water supply connection. Feedwater
shall not be introduced through open-
ings or connections provided for clean-
ing, safety relief valves, drain, pressure
gage, or temperature gage.
2) If the water supply pressure to a water
heater exceeds 75% of the set pressure
of the safety relief valve, a pressure
reducing valve is required.
3.7.5 STOP VALVES
3.7.5.1 STEAM HEATING, HOT-WATER
HEATING, AND HOT- WATER
SUPPLY BOILERS
A09 a) For Single Steam Heating Boilers
When a stop valve is used in the supply
pipe connection of a single steam boiler,
there shall be one installed in the return
pipe connection.
A09 b) For Single Hot Water Heating & Hot Water
Supply Boilers
1) Stop valves shall be located at an ac-
cessible point in the supply and return
pipe connections as near the boiler as is
convenient and practicable, of a single
hot water boiler installation to permit
draining the boiler without emptying
the system.
2) When the boiler is located above the
system and can be drained without
draining the system stop valves required
in paragraph 3.7.5.1 b) 1 ) may be elimi-
nated.
boilers connected to a common system.
See Figures 3.7.5 a), 3.7.5 b), and 3.7.5 c).
d) Types of Stop Valve(s)
1 ) All valves or cocks shall conform with
the applicable portions of an accept-
able code of construction and may be
ferrous or nonferrous.
2) The minimum pressure rating of all
valves or cocks shall be at least equal
to the pressure stamped upon the boiler,
and the temperature rating of such
valves or cocks, including all internal
components, shall be not less than
250°F(121°C).
3) Valves or cocks shall be flanged, thread-
ed or have ends suitable for welding or
brazing.
4) All valves or cocks with stems or
spindles shall have adjustable pressure-
type packing glands and, in addition,
all plug-type cocks shall be equipped
with a guard or gland. The plug or other
operating mechanism shall be distinctly
marked in line with the passage to in-
dicate whether it is opened or closed.
5) All valves or cocks shall have tight clo-
sure when under boiler hydrostatic test
pressure.
A09
3.7.5.2
POTABLE WATER HEATERS
A07
Stop valves shall be installed in the supply
and discharge pipe connections of a water
heater installation to permit draining the water
heater without emptying the system. See Figure
3.7.5(d).
3.7.6
RETURN PIPE CONNECTIONS
A09 c) For Multiple Boiler Installations
A stop valve shall be used in each supply-
and-return pipe connection of two or more
The return pipe connections of each boiler
supplying a gravity return steam heating
system shall be so arranged as to form a loop
substantially as shown in Figure 3.7.5-b
4 i
NATIONAL BOARD INSPECTION CODE • PART 1
INSTALLATION
so that the water in each boiler cannot be
forced out below the safe water level.
b) For hand-fired boilers with a normal grate
line, the recommended pipe sizes detailed
as "A" in Figures 3.7.5-a and 3.7.5-b are
NPS 1-1/2 (DN 40) for 4 sq. ft (0.37 sq. m)
or less firebox area at the normal grate line,
NPS 2-1/2 (DN 65) for areas more than 4
sq. ft (0.37 sq. m) up to 1 4.9 sq. ft (1 .38 sq.
m), and NPS 4 (DN 1 00) for 1 5 sq. ft (1 .39
sq. m) or more.
c) For automatically-fired boilers that do not
have a normal grate line, the recommended
pipe sizes detailed as "A" in Figures 3.7.5-
a and 3.7.5-b are NPS 1-1/2 (DN 40) for
boilers with minimum safety valve relieving
capacity 250 Ib/hr (1 1 3 kg/hr) or less, NPS
2-1/2 (DN 65) for boilers with minimum
safety valve relieving capacity from 251
Ib/hr (114 kg/hr) to 2000 Ib/hr (907 kg/hr),
inclusive, and NPS 4 (DN 100) for boil-
ers with more than 2000 Ib/hr (907 kg/hr)
minimum safety valve relieving capacity.
d) Provision shall be made for cleaning the
interior of the return piping at or close to the
boiler. Washout openings should be used
for return pipe connections and the wash-
out plug placed in a tee or a cross so that
the plug is directly opposite and as close
as possible to the opening in the boiler.
FIGURE 3.7.5-a
Steam boilers in battery
pumped return — acceptable piping installation
Steam main
Heating
supply
From receiver lank
General Note:
Return connections shown for a multiple boiler installation may not always
ensure that the system will operate properly. In order to maintain proper water levels in multiple
boiler installations, it may he necessary to install supplementary controls or suitable devices.
Note:
(1) Recommended for 1 in. (25 mm) and larger safety valve discharge.
42
NATIONAL BDARD INSPECTION CODE • PART 1 — INSTALLATION
A07
FIGURE 3.7.5-d
Storage Potable Water Heaters in Battery - Acceptable Piping installation
rt—fy — w * — i-
^<-
-Ja — *-k
i>-
To Open Drain
Cold Water Supply
4 — &th
$? c y,
Water Heater with Top
-i i/i-^*-
Drain Valve with
Suitable Drain
Point of Use
A
l/ D C ^
Drain Valve
(1)
system may be gravity or pump actuated.
A07
FIGURE 3.7.5-e
Flow Through Potable Water Heater Without Provision for Piping Expansion - Acceptable
Piping Installation
-ut-
-* ^
Flow switch on
&
o S^
-Drain valve
-Optical
reci
line
45
NATIPNAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
3.7.7 BOTTOM BLOWOFF AND
DRAIN VALVES
rating of such valves and cocks shall not
be less than 250°F (121°C).
3.7.7.1 STEAM HEATING, HOT-WATER
HEATING, AND HOT-WATER
SUPPLY BOILERS
a) Bottom Blowoffs
1) Each steam boiler shall have a bottom
blowoff connection fitted with a valve
or cock connected to the lowest water
space practicable with a minimum
size as shown in Table 3.7.7.1. The
discharge piping shall be full size to
the point of discharge.
2) Boilers having a capacity of 25 gallons
(95 I) or less are exempt from the above
requirements, except that they shall
have a NPS 3/4 (DN 20) minimum drain
valve.
b) Drains
1) Each steam or hot-water boiler shall
have one or more drain connections,
fitted with valves or cocks connecting
to the lowest water containing spaces.
All parts of the boiler must be capable
of being drained (the boiler design will
dictate the number and size of drains).
The minimum size of the drain piping,
valves, and cocks shall be NPS 3/4 (DN
20). The discharge piping shall be full
size to the point of discharge.
2) When the blowoff connection is located
at the lowest water containing space,
a separate drain connection is not re-
quired.
c) Minimum Pressure Rating
The minimum pressure rating of valves
and cocks used for blowoff or drain pur-
poses shall beat least equal to the pressure
stamped on the boiler but in no case less
than 30 psig (200 kPa). The temperature
TABLE 3.7.7.1
Size of bottom blowoff piping, valves, and
cocks
Minimum Required
Safety Valve Capacity, lbs.
of steam/hr (Note 1)
Blowoff Piping,
Valve, and Cock
Sizes, in. (mm)(min.)
up to 500
(up to 227 kg)
3/4
(19)
501 to 1,250
(over 227 kg to 567 kg)
1
(25)
1,251 to 2,500
(over 567 kg to 1134 kg)
1-1/4
(32)
2,501 to 6,000
(over 1134 kg to 2722 kg)
1-1/2
(38)
6,001 and larger
(over 2722 kg)
2
(50)
Note 1 : To determine the discharge capacity of
the safety relief valves in terms of total energy
absorbed, use 1 lb steam per hour per 1 000 Btu (1
kg steam per hour per 2326 kj).
3.7.7.2 POTABLE WATER HEATERS
Drain Valve
a) Each water heater shall have a bottom
drain pipe connection fitted with a valve
or cock connected with the lowest water
space practicable. The minimum size bot-
tom valve shall be NPS 3/4 (DN 20).
b) Any discharge piping connected to the bot-
tom drain connection shall be full size to
the point of discharge. See Figures 3.7. 5-d A07
and 3.7.5-e.
46
NATIONAL BOARD INSPECTION CODE • PART 1
INSTALLATION
3.7.8
3.7.8.1
MODULAR STEAM HEATING
AND HOT-WATER HEATING
BOILERS
INDIVIDUAL MODULES
a) The individual modules shall comply with
all the requirements of the code of construc-
tion and this paragraph. The individual mod-
ules shall be limited to a maximum input of
A07 400,000 Btu/hr (117 kW/hr), gas 3 gal./hr
(1 1 .4 l/hr), oil or 1 1 7 kW (electricity).
b) Each module of a modular steam heating
boiler shall be equipped with:
1) Safety valve, see 3.9.2.
2) Blowoff valve, see 3.7.7.1 (a).
3) Drain valve, see 3.7.7.1(b).
c) Each module of a modular hot-water heat-
ing boiler shall be equipped with:
1) Safety relief valve, see 3.9.3.
2) Drain valve, see 3.7.7.1(b).
3.7.8.2 ASSEMBLED MODULAR
BOILERS
a) The individual modules shall be manifolded
together at the job-site without any inter-
vening valves.
b) The assembled modular steam heating
boiler shall also be equipped with:
1) Feedwater connection, see Figures
3.7.5-a and 3.7.5-b.
2) Return pipe connection, see Figures
3.7.5-a and 3.7.5-b.
c) The assembled modular hot water boiler
shall also be equipped with:
1) Makeup water connection, see Figure
3.7.5-c.
2) Provision for thermal expansion, see
Figures 3.7.5-c and Table 3.7.9.1 -a.
3) Stop valves, see Figure 3.7.5-c (treat-
ing the assembled modular boiler as a
single unit).
3.7.9 PROVISIONS FOR THERMAL
EXPANSION
3.7.9.1 EXPANSION TANKS AND
PIPING FOR STEAM HEATING,
HOT-WATER HEATING AND
HOT-WATER SUPPLY BOILERS A09
a) Expansion Tanks for Hot-Water Heating,
and Hot-Water Supply Boilers
All hot-water heating systems incorporating
hot-water tanks or fluid relief columns shall
be so installed as to prevent freezing under
normal operating conditions.
1 ) Heating Systems With Open Expansion
Tank
An indoor overflow from the upper
portion of the expansion tank shall be
provided in addition to an open vent,
the indoor overflow shall be carried
within the building to a suitable plumb-
ing fixture or drain.
2) Closed Heating Systems
An expansion tank shall be installed
that will be consistent with the volume
and capacity of the system. If the system
is designed for a working pressure of 30
psig (200 kPa) or less, the tank shall be
suitably designed for a minimum hydro-
static test pressure of 75 psig (520 kPa).
Expansion tanks for systems designed to
operate above 30 psig (200 kPa) shall
be constructed in accordance with
an acceptable code of construction.
Provisions shall be made for draining
the tank without emptying the system.
Except for prepressurized tanks, the
47
NATIONAL. BOARD INSPECTION CODE • PART 1
INSTALLATION
A09
minimum capacity of the closed-type
expansion tank should be determined
from Tables 3.7.9.1 -a and 3.7.9.1 -b or
from the following formula where the
necessary information is available:
US Customary:
V t = (0.0004 7T - 0.0466)V
(P?P f )-(P/P)
where,
v ,=
minimum volume of tanks,
gallons
V =
s
volume of system, not
including tanks, gallons
T =
(t2-t1)°F
A07
t, =
lower temperature
A07
t 2 =
higher temperature
P =
a
atmospheric pressure, psia
P f =
fill pressure, psia
P =
maximum operating
pressure, psia
A07
Metric
v,=
(0.0007387- 0.0.3348)V s
(P/PJ - (P/P
where,
V
T =
P =
a
minimum volume of tanks,
liters
volume of system, not
including tanks, liters
average operating
temperature, °C
atmospheric pressure, kPa
fill pressure, kPa
maximum operating
pressure, kPa
3)
Hot-Water Supply Systems
If a system is equipped with a check
valve or pressure-reducing valve in
the cold water inlet line, consideration
should be given to the installation of an
airtight expansion tank or other suitable
air cushion. Otherwise, due to the ther-
mal expansion of the water, the safety
relief valve may lift periodically. If an
expansion tank is provided, it shall be
Table 3.7.9.1 -a
Expansion Tank Capacities for Gravity Hot-
Water Systems
(Based on two-pipe system with average operating
water temperature 1 70°F (77°C), using cast-iron
column radiation with heat emission rate
150 Btu/hr sq. ft. (473 W/sq. m) equivalent direct
radiation.)
Installed Equivalent
Direct Radiation, sq.
ft. (sq. m) (Note)
No.
Tank Capacity,
gallon (1)
up to 350 (33)
1 8 (68)
up to 450 (42)
21 (80)
up to 650 (60)
24(91)
up to 900 (84)
30(114)
up to 1,100 (102)
35(132)
up to 1,400 (130)
40(151)
up to 1,600 (149)
2
60 (228)
up to 1,800 (167)
2
60 (228)
up to 2,000 (186)
2
70 (264)
up to 2,400 (223)
2
80 (302)
Note: For systems with more than 2,400 sq. ft.
(223 sq. m) of installed equivalent direct water
radiation, the required capacity of the cushion
tank shall be increased on the basis of 1 gallon
(3.81 1) tank capacity/33 sq. ft. (3 sq. m) of
additional equivalent direct radiation.
constructed in accordance with an ac-
ceptable code of construction. Except
for prepressurized tanks, which should
be installed on the cold water side,
provisions shall be made for draining
the tank without emptying the system.
See Figures 3.7.5-d and 3.7.5-e for a
typical acceptable installation.
b) Piping for Steam Heating, Hot-water Heat-
ing, and Hot-water Supply Boilers
Provisions shall be made for the expansion
and contraction of steam and hot water
mains connected to boiler(s) so there will be
no undue strain transmitted to the boiler(s).
See Figures 3.7.5-a, 3.7.5-b, and 3.7.5-c for
typical schematic arrangements of piping
incorporating strain absorbing joints for
steam and hot-water heating boilers.
4B
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
Table 3.7.9.1 -b
Expansion Tank Capacities for Forced Hot-
Water Systems (Note)
Table 3.7.9.2
Expansion Tank Capacities for a Potable
Water Heater (Note)
A09
(Based on average operating water temperature
195°F [91 °C], fill pressure 12 psig [83 kPa], and
maximum operating pressure 29 psig [200 kPa])
Tank Capacities, gal (I)
System
Volume,
gal (I)
Prepressurized
Diaphragm
type
Nonpressurized
type
100(380)
9(34)
18(57)
200 (760)
1 7 (64)
30(114)
300(1140)
25 (95)
45 (1 70)
400(1514)
33(125)
60 (227)
500(1890)
42(159)
75 (284)
1,000(3790)
83 (315)
150(568)
2,000 (7570)
165 (625)
300(1136)
Note: System volume includes volume of water in
boiler, radiation, and piping, not including the ex-
pansion tank. Expansion tank capacities are based
on an acceptance factor of 0.4027 for prepressur-
ized types and 0.222 for nonpressurized types.
For other cases or metric calculations see Chapter
1 2 of the 1 996 HVAC Systems and Equipment
Volume of the ASHRAE Handbook.
3.7.9.2 EXPANSION TANKS AND
PIPING FOR POTABLE WATER
HEATERS
a) Expansion Tanks
If a system is equipped with a check valve
or pressure-reducing valve in the cold water
inlet line, consideration should be given to
the installation of an airtight expansion tank
or other suitable air cushion. Otherwise,
due to the thermal expansion of the water,
the safety relief valve may lift periodically.
If an expansion tank is provided, it shall be
constructed in accordance with an accept-
able code of construction. The minimum
capacity of the expansion tank may be
A09 determined from Table 3.7.9.2. (See Figures
3.7.5-d and 3.7.5-e for a typical acceptable
Tank Capacities, gal. (I)
System
Volume,
gal. (I)
Prepressurized
Diaphragm
type
Nonpressurized
type
50(190)
1 (4)
3(11)
100(380)
2(8)
6(23)
200 (760)
3(11)
12 (45)
300(1140)
4(15)
18(68)
400(1514)
5(19)
24(91)
500(1890)
6(23)
30(114)
1,000(3790)
12 (45)
60 (227)
2,000 (7570)
24(91)
120(454)
Note: Capacities in this table are given as a guide
to reduce or eliminate relief valve weeping under
conditions of partial water system demands or oc-
casional water draw during recovery.
System volume includes water heater capacity plus
all piping capacity for a recirculation system or
potable water heater capacity only for a nonrecir-
culation system.
The capacities are based upon a water temperature
rise from 40°F to 1 80°F (4°C to 82°C), 60 psig
(414 kPa) fill pressure, maximum operating pres-
sure of 1 25 psig (862 kPa) 20% water recovery,
and an acceptance factor of 0.465 for prepressur-
ized types, and 0.091 56 for nonpressurized types.
For other cases or metric calculations see Chapter
1 2 of the 1 996 HVAC Systems and Equipment
Volume of the ASHRAE Handbook.
A09
installation.) Except for pre-pressurized
diaphragm-type tanks, which should be
installed on the cold water side, provisions
shall be made for draining the tank without
emptying the system.
b) Piping
Provisions shall be made for the expansion
and contraction of hot water mains con-
nected to potable water heater(s) so that A07
there will be no undue stess transmitted
to the potable water heater(s). (See Figures AQ9
3.7.5-d and 3.7.5-e for typical schematic
arrangements of piping incorporating strain
absorbing joints).
49
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
3.8
3.8.1
INSTRUMENTS, FITTINGS, AND
CONTROLS
STEAM HEATING BOILERS
3.8.1.1 STEAM GAGES
a) Each steam boiler shall have a steam gage
or a compound steam gage connected to its
steam space or to its water column or to its
steam connection. The gage or connection
shall contain a siphon or equivalent device
that will develop and maintain a water
seal that will prevent steam from entering
the gage tube. The connection shall be so
arranged that the gage cannot be shut off
from the boiler except by a cock placed in
the pipe at the gage and provided with a
tee-handle or lever-handle arranged to be
parallel to the pipe in which it is located
when the cock is open. The connections
to the boiler shall be not less than NPS 1/4
(DN 8). Where steel or wrought iron pipe
or tubing is used, the connection and ex-
ternal siphon shall be not less than NPS 1/2
(DN 1 5). The minimum size of a siphon, if
used, shall be NPS 1/4 (DN 8). Ferrous and
nonferrous tubing having inside diameters
at least equal to that of standard pipe sizes
listed above may be substituted for pipe.
b) The scale on the dial of a steam boiler gage
shall be graduated to not less than 29 psig
(200 kPa) nor more than 58 psig (400 kPa).
The travel of the pointer from psig (0 kPa)
to 29 psig (200 kPa) pressure shall be at
least 3 in. (76 mm).
3.8.1 .2 WATER GAGE GLASSES
a) Each steam boiler shall have one or more
water gage glasses attached to the water
column or boiler by means of valved fittings
not less than NPS 1/2 (DN 15), with the
lower fitting provided with a drain valve of
a type having an unrestricted drain opening
not less than NPS 1/4 (DN 8) to facilitate
cleaning. Gage glass replacement shall be
possible under pressure. Water glass fittings
may be attached directly to a boiler. Boilers
having an internal vertical height of less
than 10 in. (254 mm) should be equipped
with a water level indicator of the glass
bulls-eye type provided the indicator is of
sufficient size to show the water at both
normal operating and low-water cutoff
levels.
b) The lowest visible part of the water gage
glass shall be at least 1 in. (25 mm) above
the lowest permissible water level recom-
mended by the boiler manufacturer. With
the boiler operating at this lowest permis-
sible water level, there shall be no danger
of overheating any part of the boiler.
c) In electric boilers of the submerged elec-
trode type, the water gage glass shall be so
located to indicate the water levels both
at startup and under maximum steam load
conditions as established by the manufac-
turer.
d) In electric boilers of the resistance element
type, the lowest visible part of the water
gage shall be located at least 1 in. (25 mm)
above the lowest permissible water level
specified by the manufacturer. Each electric
boiler of this type shall also be equipped
with an automatic low-water cutoff on
each boiler pressure vessel so located as
to automatically cut off the power supply
to the heating elements before the surface
of the water falls below the visible part of
the glass.
e) Tubular water glasses on electric boilers
having a normal water content not exceed-
ing 1 00 gal. (380 I) shall be equipped with
a protective shield.
Note: Transparent material other than glass
may be used for the water gage provided
that the material will remain transparent
and has proved suitable for the pressure,
5D
NATIONAL BOARD INSPECTION CDDE • PART 1
INSTALLATION
temperature, and corrosive conditions ex-
pected in service.
3.8.1 .3 WATER COLUMN AND WATER
LEVEL CONTROL PIPES
a) The minimum size of ferrous or nonferrous
pipes connecting a water column to a steam
boiler shall be NPS 1 (DN 25). No outlet
connections, except for damper regulator,
feedwater regulator, steam gages, or ap-
paratus that does not permit the escape of
any steam or water except for manually
operated blowdown, shall be attached to
a water column or the piping connecting a
water column to a boiler (see 3.7.4[a]) for
introduction of feedwater into a boiler). If
the water column, gage glass, low-water
fuel cutoff, or other water level control
device is connected to the boiler by pipe
and fittings, no shutoff valves of any type
shall be placed in such pipe and a cross or
equivalent fitting to which a drain valve and
piping may be attached shall be placed in
the water piping connection at every right
angle turn to facilitate cleaning. The water
column drain pipe and valve shall be not
less than NPS 3/4 (DN 20).
b) The steam connections to the water column
of a horizontal firetube wrought boiler shall
betaken from the top of the shell or the up-
per part of the head, and the water connec-
tion shall be taken from a point not above
the center line of the shell. For a cast-iron
boiler, the steam connection to the water
column shall be taken from the top of an
end section or the top of the steam header,
and the water connection shall be made on
an end section not less than 6 in. (1 52mm)
below the bottom connection to the water
gage glass.
3.8.1.4 PRESSURE CONTROL
Each automatically fired steam boiler shall be
protected from overpressure by two pressure-
operated controls.
a) Each individual steam boiler or each sys- A08
tern of commonly connected steam boilers
shall have a control that will cut off the fuel
supply when the steam pressure reaches an
operating limit, which shall be less than the
maximum allowable pressure.
b) Each individual automatically fired steam
boiler shall have a safety limit control,
with a manual reset, that will cut off the A08
fuel supply to prevent steam pressure from
exceeding the 1 5 psig (1 00 kPa) maximum
allowable working pressure of the boiler.
Each control shall be constructed to pre-
vent a pressure setting above 1 5 psig (1 00
kPa).
c) Shutoff valves of any type shall not be
placed in the steam pressure connection
between the boiler and the controls de-
scribed in (a) and (b) above. These controls
shall be protected with a siphon or equiva-
lent means of maintaining a water seal
that will prevent steam from entering the
control. The connections to the boiler shall
not be less than NPS 1/4 (DN 8), but where
steel or wrought iron pipe or tubing is used,
they shall not be less than NPS 1/2 (DN 15).
The minimum size of an external siphon
shall be NPS 1/4 (DN 8) or 3/8 in. (1 mm)
outside diameter nonferrous tubing. For
manifold connections, the minimum size
shall be as specified in the original code
of construction.
3.8.1.5 AUTOMATIC LOW-WATER FUEL
CUTOFF AND/OR WATER
FEEDING DEVICE
a) Each automatically-fired steam- or vapor-
system boiler shall have an automatic
low-water fuel cutoff so located as to auto-
matically cut off the fuel supply when the
surface of the water falls to the lowest vis-
ible part of the water gage glass. If a water
feeding device is installed, it shall be so
constructed that the water inlet valve can-
not feed water into the boiler through the
float chamber and so located as to supply
requisite feedwater.
5 1
NATIDNAL BOARD INSPECTION CODE • PART 1
INSTALLATION
b) Such a fuel cutoff or water feeding device
may be attached directly to a boiler. A fuel
cutoff or water feeding device may also be
installed in the tapped openings available
for attaching a water glass directly to a
boiler, provided the connections are made
to the boiler with nonferrous tees or Y's
not less than NPS 1/2 (DN 15) between
the boiler and water glass so that the water
glass is attached directly and as close as
possible to the boiler; the run of the tee or
Y shall take the water glass fittings, and the
side outlet or branch of the tee or Y shall
take the fuel cutoff or water feeding device.
The ends of all nipples shall be reamed to
full-size diameter.
A08 c) In addition to the requirements in a) and b)
above, a secondary low water fuel cutoff
with manual reset shall be provided on
A09 eacn automatically fired steam or vapor-
system boiler.
A08 d) Fuel cutoffs and water feeding devices
embodying a separate chamber shall have
a vertical drain pipe and a blowoff valve
not less than NPS 3/4 (DN 20), located at
the lowest point in the water equalizing
pipe connections so that the chamber and
the equalizing pipe can be flushed and the
device tested.
3.8.1.7 INSTRUMENTS, FITTINGS, AND
CONTROLS MOUNTED INSIDE
BOILER JACKETS
Any or all instruments, fittings, and controls
required by these rules may be installed inside
of boiler jackets provided the water gage and
pressure gage on a steam boiler are visible
through an opening or openings at all times.
3.8.2 HOT-WATER HEATING OR HOT-
WATER SUPPLY BOILERS
3.8.2.1 PRESSURE OR ALTITUDE GAGES
a) Each hot-water heating or hot-water supply
boiler shall have a pressure or altitude gage
connected to it or to its flow connection
in such a manner that it cannot be shut off
from the boiler except by a cock with tee
or lever handle, placed on the pipe near
the gage. The handle of the cock shall be
parallel to the pipe in which it is located
when the cock is open.
b) The scale on the dial of the pressure or alti-
tude gage shall be graduated approximately
to not less than 1-1/2 nor more than 3-1/2
times the pressure at which the safety relief
valve is set.
3.8.1.6 MODULAR STEAM HEATING
BOILERS
a) Each module of a modular steam boiler
shall be equipped with:
1) Steam gage, see 3.8.1 .1 .
2) Water gage glass, see 3.8.1 .2.
3) Pressure control, see 3.8.1 .4(a).
4) Low-water cutoff, see 3.8.1 .5.
b) The assembled modular steam heating
boiler shall also be equipped with a pres-
sure control. See 3.8.1 .4(b).
Piping or tubing for pressure or altitude
gage connections shall be of nonferrous
metal when smaller than NPS 1 (DN 25).
3.8.2.2
THERMOMETERS
Each hot-water heating or hot-water supply
boiler shall have a thermometer so located and
connected that it shall be easily readable. The
thermometer shall be so located that it shall at
all times indicate the temperature of the water
in the boiler at or near the outlet.
52
NATIONAL BOARD INSPECTION CODE • PART 1
INSTALLATION
3.8.2.3 TEMPERATURE CONTROL
Each automatically fired hot-water heating or
hot-water supply boi ler shal I be protected from
over-temperature by two temperature-operated
controls.
A08a)
A09
A08 D )
A09
Each individual hot-water heating or hot-
water supply boiler or each system of
commonly connected boilers shall have a
control that will cut off the fuel supply when
the water temperature reaches an operating
limit, which shall be less than the maximum
allowable temperature.
In addition to a) above, each individual
automatically fired hot-water heating or
hot-water supply boiler shall have a safety
limit control with manual reset that will
cut off the fuel supply to prevent the water
temperature from exceeding the maximum
allowable temperature at the boiler out-
let.
3.8.2.4
LOW-WATER FUEL CUTOFF
a) Each automatically fired hot-water boiler
shall have an automatic low-water fuel
cutoff with manual reset. The low-water
A08 fuel cutoff shall be designed for hot-water
A09 service, and it shall be so located as to
automatically cut off the fuel supply when
the surface of the water falls to the level
established in (b) below.
b) As there is no normal waterlineto be main-
tained in a hot-water boiler, any location of
the low-water fuel cutoff above the lowest
safe permissible water level established by
the boiler manufacturer is satisfactory.
A09 c) In lieu of the requirements for low-water
fuel cutoffs in paragraph a), boilers requir-
ing forced circulation to prevent overheat-
ing of the tubes, coils, or vessel, shall have
an accepted flow, and/or temperature-
sensing device to prevent burner operation
at a flow rate inadequate to protect the
boiler unit against overheating at all allow- A08
able firing rates. This safety control(s) shall
shut down the burner and prevent restarting
until an adequate flow is restored and shall
be independent of all other controls.
d) A means shall be provided for testing the
operation of the external low-water fuel
cutoff without resorting to draining the
entire system. Such means shall not render
the device inoperable except as follows. If
the means temporarily isolates the device
from the boiler during this testing, it shall
automatically return to its normal position.
The connection may be so arranged that the
device cannot be shut off from the boiler
except by a cock placed at the device and
provided with a tee or lever-handle ar-
ranged to be parallel to the pipe in which
it is located when the cock is open.
3.8.2.5 MODULAR HOT-WATER
HEATING BOILERS
a) Each module of a modular hot-water heat-
ing boiler shall be equipped with:
1) Pressure/altitude gage, see 3.8.2.1 .
2) Thermometer, see 3.8.2.2.
3) Temperature control, see 3.8.2.3(a).
b) The assembled modular hot-water heating
boiler shall be equipped with:
1) Temperature control, see 3.8.2.3(b).
2) Low-water fuel cutoff, see 3.8.2.4.
3.8.2.6 INSTRUMENTS, FITTINGS, AND
CONTROLS MOUNTED INSIDE
BOILER JACKETS
Any or all instruments, fittings, and controls
required by these rules may be installed inside
53
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
of boi ler jackets provided the thermometer and
pressure gage are visible through an opening
or openings at all times.
3.8.3 POTABLE WATER HEATERS
3.8.3.1 TEMPERATURE CONTROLS
Each individual automatically fired water
heater, in addition to the operating control
used for normal water heater operation, shall
have a separate high limit temperature actuated
combustion control that will automatically cut
off the fuel supply. The temperature range of the
high limit temperature actuated control shall
not allow a setting over 21 0°F (99°C).
a) On gas-fired water heaters, the high limit
temperature control when actuated shall
shut off the fuel supply with a shutoff
means other than the operating control
valve. Separate valves may have a common
body.
b) On electrically heated water heaters, the
high limit temperature control when actu-
ated shall cut off all power to the operating
controls.
c) On oil-fired water heaters, the high limit
temperature control when actuated shall
cut off all current flow to the burner mecha-
nism.
3.9 PRESSURE-RELIEVING VALVES
3.9.1 SAFETY VALVE REQUIREMENTS
— GENERAL
A07
The following general requirements pertain to
installing, mounting, and connecting safety
valves on boilers.
3.9.1.1 MOUNTING SAFETY AND
SAFETY RELIEF VALVES FOR
STEAM HEATING, HOT-WATER
HEATING, AND HOT-WATER
SUPPLY BOILERS
3.9.1.1.1 PERMISSIBLE MOUNTING
Safety valves and safety relief valves shall be
located at the top side 5 of the boiler. They shall
be connected directly to a tapped or flanged
opening in the boiler, to a fitting connected to
the boiler by a short nipple, to a Y-base, or to
a valveless header connecting steam or water
outlets on the same boiler. Coil- or header-type
boilers shall have the safety valve or safety relief
valve located on the steam or hot water outlet
end. Safety valves and safety relief valves shall
be installed with their spindles vertical. The
opening or connection between the boiler and
any safety valve or safety relief valve shall have
at least the area of the valve inlet.
d) On indirect water heating systems, the high
limit temperature control when activated
shall cut off the source of heat.
3.9.1.1.2 REQUIREMENTS FOR
COMMON CONNECTIONS FOR
TWO OR MORE VALVES
3.8.3.2
THERMOMETER
Each installed water heater shall have a ther-
mometer so located and connected that it shal I
be easily readable. The thermometer shall be
so located that it shall at all times indicate the
temperature of the water in the water heater at
or near the outlet.
a) When a boiler is fitted with two or more
safety valves on one connection, this con-
nection shall have a cross-sectional area
not less than the combined areas of inlet
connections of all the safety valves with
which it connects.
5 Side — The top side of the boiler shall mean the highest
practicable part of the boiler proper but in no case shall the
safety valves be located below the normal operating level and
in no case shall the safety relief valve be located below the low-
est permissable water level.
54
NATIONAL BDARD INSPECTION CODE • PART 1 — INSTALLATION
b) When a Y-base is used, the inlet area shall
be not less than the combined outlet areas.
When the size of the boiler requires a safety
valve or safety relief valve larger than NPS
4 (DN100), two or more valves having
the required combined capacity shall be
used. When two or more valves are used
on a boiler, they may be single, directly
attached, or mounted on a Y-base.
3.9.1.2 THREADED CONNECTIONS
A threaded connection may be used for attach-
ing a valve.
b) The discharge from safety or safety relief
valves shall be so arranged that there will be
no danger of scalding attendants. The safety
or safety relief valve discharge shall be
piped away from the boiler to a safe point A07
of discharge, and there shall be provisions
made for properly draining the piping. The
size and arrangement of discharge piping
shall be such that any pressure that may
exist or develop will not reduce the reliev-
ing capacity of the relieving devices below
that required to protect the boiler.
3.9.1 .6 TEMPERATURE AND PRESSURE
SAFETY RELIEF VALVES
A09
3.9.1.3 PROHIBITED MOUNTINGS
Safety and safety relief valves shall not be con-
nected to an internal pipe in the boiler.
3.9.1.4 USE OF SHUTOFF VALVES
PROHIBITED
No shutoff of any description shall be placed
between the safety or safety relief valve and
the boiler or on discharge pipes between such
valves and the atmosphere.
3.9.1 .5 SAFETY AND SAFETY RELIEF
VALVE DISCHARGE PIPING
a) A discharge pipe shall be used. Its internal
cross-sectional area shall be not less than
the full area of the valve outlet or of the total
of the valve outlets discharging thereinto,
and shall be as short and straight as pos-
sible and so arranged as to avoid undue
stress on the valve or valves. A union may
be installed in the discharge piping close to
the valve outlet. When an elbow is placed
on a safety or a safety relief valve discharge
pipe, it shall be located close to the valve
outlet downstream of the union to minimize
reaction moment stress.
Hot-water heating or supply boilers limited to
a water temperature of 2 1 0°F (99°C) may have
one or more National Board capacity certified
temperature and pressure safety relief valves
installed. The requirements of 3.9.1 .1 through
3.9.1 .5 shall be met, except as follows:
a) A Y-type fitting shall not be used.
b) If additional valves are used, they shall
be temperature and pressure safety relief
valves.
c) When the temperature and pressure safety
relief valve is mounted directly on the
boiler with no more than 4 in. (100 mm)
maximum interconnecting piping, the valve
should be installed in the horizontal posi-
tion with the outlet pointed down.
3.9.2 SAFETY VALVE REQUIREMENTS
FOR STEAM BOILERS
a) Safety valves are to be manufactured in ac-
cordance with a national or international
standard.
b) Each steam boiler shall have one or more
National Board capacity certified safety
valves of the spring pop type adjusted and
sealed to discharge at a pressure not to
exceed 15 psig (100 kPa).
55
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
c) No safety valve for a steam boiler shall be
smaller than NPS 1/2 (DN 15). No safety
valve shall be larger than NPS 4 (DN 1 00).
The inlet opening shall have an inside di-
ameter equal to, or greater than, the seat
diameter.
d) The minimum valve capacity in pounds (ki-
lograms) per hour shall be the greater of that
determined by dividing the maximum Btu
(Watts) output at the boiler nozzle obtained
by the firing of any fuel for which the unit
is installed by 1000 Btu/lb (645 W/hr/kg),
or shall be determined on the basis of the
pounds (kilograms) of steam generated
per hour per square foot (square meter)
of boiler heating surface as given in Table
3.9.2. For cast-iron boilers, the minimum
valve capacity shall be determined by the
maximum output method. In many cases
a greater relieving capacity of valves will
have to be provided than the minimum
specified by these rules. In every case, the
requirement of 3.9.2(e) shall be met.
e) The safety valve capacity for each steam
boiler shall be such that with the fuel burn-
ing equipment installed, and operated at
maximum capacity, the pressure cannot
rise more than 5 psig (34 kPa) above the
maximum allowable working pressure.
f) When operating conditions are changed,
or additional boiler heating surface is
installed, the valve capacity shall be in-
creased, if necessary, to meet the new con-
ditions and be in accordance with 3.9.2(e).
The additional valves required, on account
of changed conditions, may be installed
on the outlet piping provided there is no
intervening valve.
3.9.3 SAFETY RELIEF VALVE
REQUIREMENTS FOR HOT-
WATER HEATING OR HOT-
WATER SUPPLY BOILERS
a) Safety relief valves are to be manufactured
in accordance with a national or interna-
tional standard.
b) Each hot-water heating or hot-water sup-
ply boiler shall have at least one National
Board capacity certified safety relief valve,
of the automatic reseating type set to relieve
at or below the maximum allowable work-
ing pressure of the boiler.
c) Hot-water heating or hot-water supply
boilers limited to a water temperature not
in excess of 210°F (99°C) may have, in
lieu of the valve(s) specified in (b) above,
one or more National Board capacity certi-
fied temperature and pressure safety relief
valves of the automatic reseating type set to
relieve at or below the maximum allowable
working pressure of the boiler.
d) When more than one safety relief valve is
used on either hot-water heating or hot-
water supply boilers, the additional valves
shall be National Board capacity certified
and may have a set pressure within a range
not to exceed 6 psig (40 kPa) above the
maximum allowable working pressure of
the boiler up to and including 60 psig (41 4
kPa), and 5% for those having a maximum
allowable working pressure exceeding 60
psig (41 3 kPa).
e) No safety relief valve shall be smaller than
NPS 3/4 (DN 20) nor larger than NPS 4
(DN 1 00), except that boilers having a heat
input not greater than 15,000 Btu/hr (4.4
kW) should be equipped with a rated safety
relief valve of NPS 1/2 (DN 15).
f) The required relieving capacity, in pounds
per hour (kg/hr), of the pressure relieving
device or devices on a boiler shall be the
greater of that determined by dividing the
maximum output in Btu (Watts) at the boiler
nozzle obtained by the firing of any fuel for
56
NATIONAL BDARD INSPECTION CODE • PART 1
INSTALLATION
A08 Table 3.9.2 - Minimum Pounds of steam per hour per square foot of
Heating Surface 1 ib steam/hr/sq.ft (kg/hr/sq m)
Firetube Boilers
Watertube Boilers
Boiler heating surface
hand-fired
5(24)
6(29)
stoker-fired
7(34)
8(39)
oil, gas, or pulverized fuel-fired
8(39)
1 (49)
Waterwall heating surface
hand-fired
8(39)
8(39)
stoker-fired
1 (49)
12 (59)
oil, gas, or pulverized fuel-fired
14(68)
16(78)
Copper-finned watertubes
A08
hand-fired
4(20)
A08
stoker-fired
5 (24)
A08
oil, gas, or pulverized fuel-fired
6(29)
A07
A08
A08
A08
NOTES:
• When a boiler is fired only by a gas having a heat value not in excess of 200 Btu/cu.ft.(7.5MJ/cu. m), the mini-
mum relieving capacity should be based on the values given for hand-fired boilers above.
« The heating surface shall be computed for that side of the boiler surface exposed to the products of combustion,
exclusive of the superheating surface. In computing the heating surface for this purpose only the tubes, fireboxes,
shells, tubesheets, and the projected area of headers need to be considered, except that for vertical firetube steam
boilers, only that portion of the tube surface up to the middle gage cock is to be computed.
• For Firetube boiler units exceeding 8000 Btu/ft. 2 (9085 J/cm. 2 ) (total fuel Btu 0) Input divided by total heat-
ing surface), the factor from the table will be increased by 1 (4.88) for every 1000 Btu/ft. 2 (1136 J/cm. 2 ) above
8000 Btu/ft. 2 (9085 J/cm. 2 ) For units less than 7000 Btu/ft. 2 (7950 J/cm. 2 ), the factor from the table will be
decreased by 1 (7950 J/cm. 2 ).
• For watertube boiler units exceeding 1 6000 Btu/ft. 2 (1 81 70 J/cm. 2 )(total fuel BTU input divided by the total
heating surface) the factor from the table will be increased by 1 (4.88) for every 1 000 Btu/ft. 2 (1136 J/cm. 2 )
above 1 6000 Btu/ft. 2 (1 81 70 J/cm. 2 ). For units with less than 1 5000 Btu/ft. 2 (1 7034 J/cm. 2 ), the factor in the
table will be decreased by 1 (4.88) for every 1 000 Btu/ft. 2 (1 1 36 J/cm. 2 ) below 1 5000 Btu/ft. 2 (1 7034 J/cm. 2 ).
which the unit is installed by 1000 Btu/lb
(645 w/kg), or shall be determined on the
basis of pounds (kilograms) of steam gener-
ated per hour per square foot (square meter)
of boiler heating surface as given in Table
3.9.2. For cast-iron boilers, the minimum
valve capacity shall be determined by the
maximum output method. In many cases
a greater relieving capacity of valves will
have to be provided than the minimum
specified by these rules. In every case, the
requirements of 3.9.3(h) shall be met.
g) When operating conditions are changed,
or additional boiler heating surface is
installed, the valve capacity shall be in-
creased, if necessary, to meet the new
conditions and shall be in accordance with
3.9.3(h). The additional valves required,
on account of changed conditions, may
be installed on the outlet piping provided
there is no intervening valve.
h) Safety relief valve capacity for each boiler
with a single safety relief valve shall be
57
NATIDNAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
such that, with the fuel burning equipment
installed and operated at maximum capac-
ity, the pressure cannot rise more than 1 0%
above the maximum allowable working
pressure. When more than one safety relief
valve is used, the over pressure shall be
limited to 10% above the set pressure of
the highest set valve allowed by 3.9.3(b).
3.9.4 SAFETY RELIEF VALVE
REQUIREMENTS FOR POTABLE
WATER HEATERS
a) Each water heater shall have at least one
National Board capacity certified tempera-
ture and pressure safety relief valve. No
safety relief valve shall be smaller than NPS
3/4 (DN 20).
b) The pressure setting shall be less than or
equal to the maximum allowable working
pressure of the water heater. However, if
any of the other components in the hot-wa-
ter supply system (such as valves, pumps,
expansion or storage tanks, or piping) have
a lesser working pressure rating than the
water heater, the pressure setting for the
safety relief valve(s) shall be based upon
the component with the lowest maximum
allowable working pressure rating. If more
than one safety relief valve is used, the ad-
ditional valve(s) may be set within a range
not to exceed 1 0% over the set pressure of
the first valve.
c) The required relieving capacity in Btu/hr
(W) of the safety relief valve shall not be
less than the maximum allowable input
unless the water heater is marked with the
rated burner input capacity of the water
heater on the casing in a readily visible
location, in which case the rated burner
input capacity may be used as a basis for
sizing the safety relief valves. The relieving
capacity for electric water heaters shall be
3500 Btu/hr (1 .0 kW) per kW of input. In
every case, the following requirements shall
be met. Safety relief valve capacity for each
water heater shall be such that with the fuel
burning equipment installed and operated
at maximum capacity, the pressure cannot
rise more than 10% above the maximum
allowable working pressure.
d) If operating conditions are changed or addi-
tional heating surface is installed, the safety
relief valve capacity shall be increased,
if necessary, to meet the new conditions
and shall be in accordance with the above
provisions. In no case shall the increased
input capacity exceed the maximum allow-
able input capacity. The additional valves
required, on account of changed condi-
tions, may be installed on the outlet piping
providing there is no intervening valve.
3.9.4.1 INSTALLATION
Safety relief valves shall be installed by either
the installer or the manufacturer before a water
heater is placed in operation.
3.9.4.2 PERMISSIBLE MOUNTINGS
Safety relief valves shall be connected directly
to a tapped or flanged opening in the top of
the water heater, to a fitting connected to the
water heater by a short nipple, to a Y-base, or
to a valveless header connecting water outlets
on the same heater. Safety relief valves shall be
installed with their spindles upright and vertical
with no horizontal connecting pipe, except that,
when the safety relief valve is mounted directly
on the water heater vessel with no more than 4
in. (1 00 mm) maximum interconnecting piping,
the valve may be installed in the horizontal po-
sition with the outlet pointed down. The center
line of the safety relief valve connection shall
be no lower than 4 in. (1 00 mm) from the top
of the shell. No piping or fitting used to mount
the safety valve shall be of nominal pipe size
less than that of the valve inlet.
58
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
3.9.4.3 REQUIREMENTS FOR
COMMON CONNECTION FOR
TWO OR MORE VALVES
a) When a potable water heater is fitted with
two or more safety relief valves on one con-
nection, this connection shall have a cross-
sectional area not less than the combined
areas of inlet connections of all the safety
release valves with which it connects.
b) WhenaY-base is used, the inlet area shall be
not less than the combined outlet areas.
c) When the size of the water heater requires
a safety relief valve larger than NPS 4 (DN
100) two or more valves having the re-
quired combined capacity shall be used.
When two or more valves are used on a
water heater, they may be single, directly
attached, or mounted on aY-base.
3.9.4.4 THREADED CONNECTIONS
of the valve outlets discharging thereinto,
and shal I be as short and straight as possible
and so arranged as to avoid undue stress
on the valve or valves. When an elbow is
placed on a safety relief discharge pipe, it
shall be located close to the valve outlet.
b) The discharge from safety relief valves shall
be so arranged that there will be no danger
of scalding attendants. When the safety re-
lief valve discharge is piped away from the
water heater to the point of discharge, there
shall be provisions for properly draining
the piping and valve body. The size and ar-
rangement of discharge piping shall be such
that any pressure that may exist or develop
will not reduce the relieving capacity of
the relieving devices below that required
to protect the water heater.
3.9.5 SAFETY AND SAFETY RELIEF
VALVES FOR TANKS AND HEAT
EXCHANGERS
A threaded connection may be used for attach-
ing a valve.
3.9.5.1
STEAM TO HOT-WATER SUPPLY
3.9.4.5
PROHIBITED MOUNTINGS
Safety relief valves shall not be connected to an
internal pipe in the water heater or a cold water
feed line connected to the water heater.
3.9.4.6 USE OF SHUTOFF VALVES
PROHIBITED
When a hot-water supply is heated indirectly
by steam in a coil or pipe within the service
limitations setforth in 3.2, Definitions, the pres-
sure of the steam used shall not exceed the safe
working pressure of the hot water tank, and a
safety relief valve at least NPS 1 (DN 25), set
to relieve at or below the maximum allowable
working pressure of the tank, shall be applied
on the tank.
No shutoff of any description shall be placed
between the safety relief valve and the water
heater or on discharge pipes between such
valves and the atmosphere.
3.9.4.7 SAFETY RELIEF VALVE
DISCHARGE PIPING
a) When a discharge pipe is used, its internal
cross-sectional area shall be not less than
the ful I area of the valve outlet or of the total
3.9.5.2 HIGH TEMPERATURE WATER TO
WATER HEAT EXCHANGER
When high temperature water is circulated
through the coils or tubes of a heat exchanger
to warm water for space heating or hot-water
supply, within the service limitations set forth
in 3.2, Definitions, the heat exchanger shall
be equipped with one or more National Board
capacity certified safety relief valves set to
relieve at or below the maximum allowable
working pressure of the heat exchanger, and
59
NATIDNAL BOARD INSPECTION CODE • PART 1
INSTALLATION
of sufficient rated capacity to prevent the heat
exchanger pressure from rising more than 1 0%
above the maximum allowable working pres-
sure of the vessel.
3.9.5.3 HIGH TEMPERATURE WATER TO
STEAM HEAT EXCHANGER
When high temperature water is circulated
through the coi Is or tubes of a heat exchanger to
generate low pressure steam, within the service
limitations set forth in 3.2, Definitions, the heat
exchanger shall be equipped with one or more
National Board capacity certified safety valves
set to relieve at a pressure not to exceed 1 5 psig
(100 kPa), and of sufficient rated capacity to
prevent the heat exchanger pressure from rising
more than 5 psig (34 kPa) above the maximum
allowable working pressure of the vessel. For
heat exchangers requiring steam pressures
greater than 1 5 psig (1 00 kPa), refer to Section
2 or Section 4 of this Part.
3.10.3
BOILER INSTALLATION REPORT
a) Upon completion, inspection, and accep-
tance of the installation, the installer shall
complete and certify the Boiler Installation
Report 1-1. See 1.4.5.1.
b) The Boiler Installation Report 1-1 shall be
submitted as follows:
1 ) One copy to the Owner;
2) One copy to the Jurisdiction, if re-
quired.
3.10.4
TABLES AND FIGURES
3.10
TESTING AND ACCEPTANCE
a) Table 3.7.9.1 -a, Expansion Tank Capacities
for Gravity Hot-Water Systems
b) Table 3.7.9.1 -b, Expansion Tank Capacities
for Forced Hot-Water Systems
c) Table 3.7.9.1 -c, Expansion Tank Capacities
for a Water Heater
3.10.1
PRESSURE TEST
Prior to initial operation, the completed boiler,
individual module, or assembled module, shall
be subjected to a pressure test in accordance
with the requirements of the original code of
construction.
d) Table 3.7.7.1 , Size of Bottom Blowoff Pip-
ing, Valves, and Cocks
e) Table 3 .9.2, Minimum Pounds of Steam Per
Hour Per Square Foot of Heating Surface
f) Figure 3 .3 . 1 . 1 -a, Spacing and Weld Details
for Supporting Lugs in Pairs on Horizontal
Return Tubular Boilers
3.10.2
FINAL ACCEPTANCE
a) In addition to determining that all equip-
ment called for is furnished and installed in
accordance with the plans and specifica-
tions, all controls shall be tested by a person
familiar with the control system.
b) Before any new heating plant (or boiler) is
accepted for operation, a final (or accep-
tance) inspection by a person familiar with
the system shall be completed and all items
of exception corrected.
g) Figure 3.3.1 .1 -b, Welded Bracket Connec-
tion for Horizontal-Return Tubular Boilers
h) Figure 3.7.5-a, Steam Boilers in Battery -
Pumped Return -Acceptable Piping Instal-
lation
i) Figure 3.7.5-b, Steam Boilers in Battery -
Gravity Return - Acceptable Piping Instal-
lation
)) Figure 3.7. 5-c, Hot-Water Boilers in Battery
-Acceptable Piping Installation
SO
N
ATIDNAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
k) Figure 3 .7.5-6, Storage Potable Water Heat-
ers in Battery - Acceptable Piping Installa-
tion
I) Figure 3.7. 5-e, FlowThrough Potable Water
Heater Without Provision for Piping Expan-
sion-Acceptable Piping Installation
e i
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
G2
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
4.4.2 PRESSURE INDICATING
DEVICES
The need for pressure indicating devices should
be considered in the design of the pressure
vessel, and when required, the scale on the
dial of the pressure gage shall be at least 25%
above the highest set pressure of the pressure
relief device.
4.5.3
LOCATION
4.5
PRESSURE RELIEF DEVICES
All pressure vessels shall be protected by pres-
sure relief devices in accordance with the fol-
lowing requirements.
4.5.1
DEVICE REQUIREMENTS
a) Pressure relief devices are to be manu-
factured in accordance with a national or
international standard and be certified for
capacity (or resistance to flow for rupture
disk devices) by the National Board.
b) Dead weight or weighted lever pressure
relief valves shall not be used.
c) An unfired steam boiler shall be equipped
with pressure relief valves as required in
Section 2 of this Part. (See 2.9).
d) Pressure relief devices shall be selected
(i.e., material, pressure, etc.) and installed
such that their proper functioning will not
be hindered by the nature of the vessel's
contents.
4.5.2
NUMBER OF DEVICES
At least one device shall be provided for protec-
tion of a pressure vessel. Pressure vessels with
multiple chambers with different maximum al-
lowable working pressures shall have a pressure
relief device to protect each chamber under the
most severe coincident conditions.
a) The pressure relief device shall be installed
directly on the pressure vessel, unless the
source of pressure is external to the vessel
and is under such positive control that the
pressure cannot exceed the maximum over- A09
pressure permitted by the original code of
construction and the pressure relief device
cannot be isolated from the vessel, except
as permitted by 4.5.6 e) 2).
b) Pressure relief devices intended for use in
compressible fluid service shall be con-
nected to the vessel in the vapor space
above any contained liquid or in the piping
system connected to the vapor space.
c) Pressure relief devices intended for use in
liquid service shall be connected below the
normal liquid line.
4.5.4
CAPACITY
a) The pressure relief device(s) shall have suf-
ficient capacity to ensure that the pressure
vessel is not exposed to pressure greater
than that specified in the original code of
construction.
b) If an additional hazard can be created by
exposure of a pressure vessel to fire or
other unexpected source of external heat,
supplemental pressure relief devices shall
be installed to provide any additional ca-
pacity that should be required.
c) Vessels connected together by a system of
piping not containing valves that can isolate
any pressure vessel should be considered
as one unit when determining capacity
requirements.
d) Heat exchangers and similar vessels shall
be protected with a pressure relief device
of sufficient capacity to avoid overpressure
in case of internal failure.
e) When a non-reclosing device is installed
65
NATIONAL BOARD INSPECTION CODE • PART 1
INSTALLATION
between a pressure relief valve and the
pressure vessel, the reduction in capacity
due to installation of the non-reclosing
device shall be determined in accordance
with the code of construction by use of
a National Board certified Combination
Capacity Factor (CCF). For rupture disks,
if a certified combination capacity factor
is not available, the capacity of the pres-
sure relief valve shall be multiplied by 0.9
and this value used as the capacity of the
combination installation.
f) The owner shall document the basis for
selection of the pressure relief devices
used, including capacity, and have such
calculations available for review by the
Jurisdiction.
b) A non-reclosing device installed between a
pressure vessel and a pressure relief valve
shall meet the requirements of 4.5.6(a).
c) The opening in the pressure vessel wall
shall be designed to provide unobstructed
flow between the vessel and its pressure
relief device.
d) When two or more required pressure relief
devices are placed on one connection, the
inlet cross-sectional area of this connection
shall be sized either to avoid restricting
flow to the pressure relief devices or made
at least equal to the combined inlet areas
of the pressure relief devices connected to
it. The flow characteristics of the upstream
system shall satisfy the requirements of
4.5.6(a).
4.5.5
SET PRESSURE
a) When a single pressure relief device is used,
the set pressure marked on the device shall
not exceed the maximum allowable work-
ing pressure.
b) When more than one pressure relief device
is provided to obtain the required capacity,
only one pressure relief device set pressure
needs to be at the maximum allowable
working pressure. The set pressures of the
additional pressure relief devices shall be
such that the pressure cannot exceed the
overpressure permitted by the code of con-
struction.
4.5.6 INSTALLATION AND
DISCHARGE PIPING
REQUIREMENTS
a) The opening through all pipe and fittings
between a pressure vessel and its pressure
relief device shall have at least the area of
the pressure relief device inlet. The char-
acteristics of this upstream system shall be
such that the pressure drop will not reduce
the relieving capacity below that required
or adversely affect the proper operation of
the pressure relief device.
e) There shall be no intervening stop valves
between the vessel and its pressure relief
device(s), or between the pressure relief
device(s) and the point of discharge, except
under the following conditions:
1) When these stop valves are so con-
structed or positively controlled that
the closing of the maximum number of
block valves at one time will not reduce
the pressure relieving capacity below
the required relieving capacity; or,
2) Upon specific acceptance of the Ju-
risdiction, when necessary for the
continuous operation of processing
equipment of such a complex nature
that shutdown of any part is not fea-
sible, a full area stop valve between a
pressure vessel and its pressure relief
device should be provided for inspec-
tion and repair purposes only. This stop
valve shall be arranged so that it can
be locked or sealed open, and it shall
not be closed except by an authorized
person who shall remain stationed there
during that period of operation while
the valve remains closed. The valve
shall be locked or sealed in the open
position before the authorized person
leaves the station.
66
NATIONAL BDARD INSPECTION CODE • PART 1
INSTALLATION
3) A full area stop valve should also be
placed on the discharge side of a pres-
sure relief device when its discharge
is connected to a common header
for pressure relief devices to prevent
discharges from these other devices
from flowing back to the first device
during inspection and repair. This stop
valve shall be arranged so that it can
be locked or sealed open, and it shall
not be closed except by an authorized
person who shall remain stationed there
during that period of operation while
the valve remains closed. The valve
shall be locked and sealed in the open
position before the authorized person
leaves the station. This valve shall only
be used when a stop valve on the inlet
side of the pressure relief device is first
closed.
4) A pressure vessel in a system where
the pressure originates from an out-
side source should have a stop valve
between the vessel and the pressure
relief device, and this valve need not
be sealed open, provided it also closes
off that vessel from the source of the
pressure.
A09 5) Pressure vessels designed for human
occupancy (such as decompression
or hyperbaric chambers) shall be pro-
vided with a quick opening stop valve
between the pressure vessel and its
pressure relief valve. The stop valve
shall be normally sealed open with a
frangible seal and be readily accessible
to the pressure relief attendant.
f) Pressure relief device discharges shall be
arranged such that they are not a hazard to
personnel or other equipment and, when
necessary, lead to a safe location for dis-
posal of fluids being relieved.
g) Discharge lines from pressure relief devices
shall be designed to facilitate drainage or
be fitted with drains to prevent liquid from
collecting in the discharge side of a pres-
sure relief device. The size of discharge
lines shall be such that any pressure that
may exist or develop will not reduce the
relieving capacity of the pressure relief
device or adversely affect the operation of
the pressure relief device.
h) Pressure relief devices shall be installed so
they are readily accessible for inspection,
repair, or replacement.
4.6
TESTING AND ACCEPTANCE
a) The installer shall exercise care during
installation to prevent loose weld mate-
rial, welding rods, small tools, and miscel-
laneous scrap metal from getting into the
vessel. The installer shall inspect the interior
of the vessel and its appurtenances where
possible prior to making the final closures
for the presence of foreign debris.
b) The completed pressure vessel shall be
pressure tested in the shop or in the field
in accordance with the original code of
construction. When required by the Juris-
diction, owner or user, the Inspector shall
witness the pressure test of the completed
installation, including piping to the pressure
gage, pressure relief device, and, if present,
level control devices.
67
NATIONAL BDARD INSPECTION CODE • PART 1 — INSTALLATION
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NATIONAL BOARD INSPECTION CODE • PART 1
INSTALLATION
5.2.5
MATERIALS
5.2.9
BOLTING
A08
All materials for piping and its appurtenances
shall comply with the requirements of the code
of construction.
5.2.6
HANGERS AND SUPPORTS
A07 Support of piping shall consider loads (includ-
ing wind and seismic loads) imposed on equip-
ment or existing piping to which it is attached.
Non-piping attachments such as ladders and
walkways, equipment supports, temporary
supports, structural supports, etc., shall not be
connected to the piping unless such loads have
been considered in the design of the piping and
its supports. Design of hangers and supports
for piping shall consider loads imposed by
hydrostatic pressure testing. The installer shall
remove pins from non-rigid hangers and seal
plugs from hydraulic snubbers and temporary
supports used for installation prior to placing
the piping in service.
5.2.7
PROTECTION AND CLEANING
The installer shall exercise care during instal-
lation to prevent loose weld material, welding
rods, small tools, and miscellaneous scrap
metal from getting into the piping. The installer
shall inspect, and where necessary clean the in-
terior of the piping and its appurtenances where
possible, prior to making the final closures for
the presence of foreign debris.
All mechanical joints and connections shall
conform to manufacturers' installation instruc-
tions and recognized standards acceptable to
the Jurisdiction having authority.
5.3
PRESSURE RELIEF DEVICES
When required by the original code of con-
struction, piping shall be protected by pressure
relief devices in accordance with the following
requirements.
5.3.1
DEVICE REQUIREMENTS
5.2.8
WELDING AND BRAZING
a) Pressure relief devices are to be manu-
factured in accordance with a national or
international standard and be certified for
capacity (or resistance to flow for rupture
disc devices) by the National Board.
1) In certain cases piping standards per-
mit the use of regulators, which may
include integral pressure relief valves
to limit the pressure in a piping system.
In this case, capacity certification of the
pressure relief valve is not required.
b) Dead weight or weighted lever pressure
relief devices shall not be used.
c) Pressure relief devices shall be selected
(i.e., material, pressure, etc.) and installed
such that their proper functioning will not
be hindered by the nature of the piping
system's contents.
The installer should consider the impact of
performing any preheating, welding, brazing,
or postweld heat treatment on valves, instru-
mentation, or other heat sensitive equipment
and, where appropriate, review the equipment
manufacturer's recommended installation pro-
cedures prior to performing the work.
5.3.2
NUMBER OF DEVICES
At least one pressure relief device shall be pro-
vided for protection of a piping system. A pres-
sure relief device installed on a pressure vessel
or other component connected to the piping
system should be used to meet this require-
ment. Portions of piping systems with different
maximum allowable working pressures shall
have a pressure relief device to protect each
portion separately.
7 1
NATIONAL BOARD INSPECTION CODE • PART 1
INSTALLATION
5.3.3
LOCATION
Pressure relief devices, except those covered by
Sections 2 and 3 of this Part, may be installed
at any location in the system provided the
A09 pressure in any portion of the system cannot
exceed the maximum overpressure permitted
by the original code of construction. Pres-
sure drop to the pressure relief device under
flowing conditions shall be considered when
determining pressure relief device location.
A09 The pressure-relief device shall not be isolated
from the piping system except as permitted by
5.3.6 e).
5.3.4
CAPACITY
a) The pressure relief device(s) shall have suf-
ficient capacity to ensure that the piping is
not exposed to pressures greater than that
specified in the original code of construc-
tion.
b) When a non-reclosing device is installed
between a pressure relief valve and the
pipe, the reduction in capacity due to in-
stallation of the non-reclosing device shall
be determined in accordance with the code
of construction by use of a National Board
certified Combination Capacity Factor
(CCF). For rupture disks, if a certified com-
bination capacity factor is not available, the
capacity of the pressure relief valve shall be
multiplied by 0.9 and this value used as the
capacity of the combination installation.
c) The owner shall document the basis for
selection of the pressure relief devices
used, including capacity, and have such
calculations available for review by the
Jurisdiction, when required.
5.3.5
SET PRESSURE
When a single pressure relief device is used,
the set pressure marked on the device shall
not exceed the maximum allowable work-
ing pressure, except when allowed by the
original code of construction.
b) When more than one pressure relief device
is provided to obtain the required capacity,
only one pressure relief device set pressure
needs to be at the maximum allowable
working pressure. The set pressures of the
additional pressure relief devices shall be
such that the pressure cannot exceed the
overpressure permitted by the code of con-
struction.
5.3.6 INLET AND DISCHARGE PIPING
REQUIREMENTS
a) The opening through all pipes and fittings
between a piping system and its pressure
relief device shall have at least the area of
the pressure relief device inlet. The char-
acteristics of this upstream system shall be
such that the pressure drop will not reduce
the relieving capacity below that required
or adversely affect the operation of the pres-
sure relief device.
b) A non-reclosing device installed between
a piping system and a pressure relief valve
shall meet the requirements of 5.3.6(a).
c) The opening in the pipe shall be designed
to provide unobstructed flow between the
pipe and its pressure relief device.
d) When two or more required pressure relief
devices are placed on the connection, the
inlet cross-sectional area of this connection
shall be sized either to avoid restricting
flow to the pressure relief devices or made
at least equal to the combined inlet areas
of the pressure relief devices connected to
it. The flow characteristics of the upstream
system shall satisfy the requirements of
5.3.6(a).
e) There shall be no intervening stop valves
between the piping system and its pressure
relief device(s), or between the pressure
relief device(s) and the point of discharge
except under the following conditions:
72
NATIDNAL BOARD INSPECTION CODE • PART 1
INSTALLATION
3)
When these stop valves are so con-
structed or positively controlled that
the closing of the maximum number of
block valves at one time will not reduce
the pressure relieving capacity below
the required relieving capacity; or,
Upon specific acceptance of the Ju-
risdiction, when necessary for the
continuous operation of processing
equipment of such a complex nature
that shutdown of any part is not fea-
sible, a full area stop valve between
a piping system and its pressure relief
device should be provided for inspec-
tion and repair purposes only. This stop
valve shall be arranged so that it can
be locked or sealed open and it shall
not be closed except by an authorized
person who shall remain stationed there
during that period of operation while
the valve remains closed. The valve
shall be locked or sealed in the open
position before the authorized person
leaves the station.
A full area stop valve may be placed on
the discharge side of a pressure relief
device when its discharge is connected
to a common header for pressure relief
devices to prevent discharges from
these other devices from flowing back
to the first device during inspection and
repair. This stop valve shall be arranged
so that it can be locked or sealed open,
and it shall not be closed except by an
authorized person who shall remain
stationed there during that period of op-
eration while the valve remains closed.
The valve shall be locked or sealed in
the open position before the authorized
person leaves the station. This valve
shall only be used when a stop valve
on the inlet side of the pressure relief
device is first closed.
provided it also closes off that vessel
from the source of pressure.
f) Pressure relief device discharges shall be
arranged such that they are not a hazard to
personnel or other equipment and, when
necessary, lead to a safe location for dis-
posal of fluids being relieved.
g) Discharge lines from pressure relief devices
shall be designed to facilitate drainage or
be fitted with drains to prevent liquid from
collecting in the discharge side of a pres-
sure relief device. The size of discharge
lines shall be such that any pressure that
may exist or develop will not reduce the
relieving capacity of the pressure relief
device or adversely affect the operation of
the pressure relief device.
h) The reaction forces due to discharge of A09
pressure relief devices shall be considered
in the design of the inlet and discharge
piping.
I) Pressure relief devices shall be installed so A09
they are accessible for inspection, repair,
or replacement.
5.4 EXAMINATION, INSPECTION,
AND TESTING
The owner shall ensure that all examinations,
inspections, and tests required by the code
of construction have been performed prior to
operation.
4) A piping system where the pressure
originates from an outside source
should have a stop valve between the
system and the pressure relief device,
and this valve need not be sealed open,
73
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
74
NATIONAL BOARD INSPECTION CODE • PART 1
INSTALLATION
A07 b) Design documentation, called the "De-
rate Curve," is required which dictates the
maximum allowable operating parameters
as shell thickness is reduced (see Figure
S1 .1 ). Calculations, used to determine those
A07 parameters, are in accordance with ASME
Code requirements for primary membrane
stress by the vessel manufacturer or design
criteria based on relevant stress categories,
e.g., fatigue and maximum principal stress.
Calculation of these parameters requires
that the respective stresses, resulting from
the imposed loads, be compared to the
appropriate material strength properties.
Hence, knowledge of the applied stresses in
the shell and the tensile and fatigue proper-
ties of the material are essential.
c) Yankee dryers are subjected to a variety of
loads that create several categories of stress.
Yankee dryers are designed such that the
stress of greatest concern occurs at the
A07 centerline of the shell.
1) Steam Pressure Load — The internal
steam pressure is one of the principal
design loads applied to the Yankee
dryer. The steam pressure expands the
shell radially, causing a predominately
circumferential membrane tensile
stress. Because the shell is constrained
radially by the heads at either end of the
shell, the steam pressure also causes a
primary bending stress in the vicinity of
the head-to-shell joint. The ends of the
shell are in tension on the inside and
compression on the outside due to the
steam pressure. The steam pressure also
causes a bending stress in the heads.
2) Inertia Load — The rotation of the
Yankee dryer causes a circumferential
membrane stress in the shell similar to
that caused by the pressure load. This
stress is included in the design of the
shell and increases with dryer diameter
and speed.
3) Thermal Load — The wet sheet, applied A07
to the shell, causes the outside surface
to cool and creates a thermal gradient
through the shell wall. This thermal
gradient results in the outside surface
being in tension and the inside surface
in compression. With this cooling, the
average shell temperature is less than
the head temperature, which creates
bending stresses on the ends of the
shell and in the heads. The ends of the
shell are in tension on the outside and
compression on the inside.
a. Other thermal loadings also oc-
cur on a Yankee dryer. The use of
full-width showers for a variety of
papermaking purposes affects the
shell similar to a wet sheet. The use
of edge sprays produce high bend-
ing stress in the ends of the shell
due to the mechanical restraint of
the heads.
b. Warm-up, cool-down, hot air im-
pingement from the hood, moisture
profiling devices, fire fighting, and
wash-up can all produce non-uni-
form thermal stresses in the pres-
sure containing parts of the Yankee
dryer. Heating or cooling different
portions of the Yankee dryer at dif-
ferent rates causes these non-uni-
form stresses.
4) Nip Load — The nip load from the A07
contacting pressure roll(s) results in an
alternating, high cycle, bending stress
in the shell. This stress is greatest at
the centerline of the shell. The load of
the pressure roll deflects the shell radi-
ally inward causing a circumferential
compressive stress on the outside sur-
face and a tensile stress on the inside.
Because the shell has been deflected
inward atthe pressure roll nip, it bulges
outward about 30 degrees on each side
of the nip. The outward bulge causes a
tensile stress on the outside shell sur-
79
NATIONAL BDARD INSPECTION CODE • PART 1 — INSTALLATION
S1.4
face at that location and a correspond-
ing compressive stress on the inside.
Since the shell is passing under the
pressure roll, its surface is subjected to
an alternating load every revolution.
ASME CODE PRIMARY
MEMBRANE STRESS CRITERIA
A07
Yankee dryers are typically designed and
fabricated in accordance with Section VIII,
Division 1, of the ASME Pressure Vessel
Code. The maximum allowable stress for
cast iron is specified in UCI-23 and UC-22
of the ASME Code.
b) Section VIII, Division 1, requires design
stresses to be calculated such that any
combination of loading expected to occur
simultaneously during normal operation of
the Yankee dryer will not result in a general
primary stress exceeding the maximum
allowable stress value of the material. In
the ASME Code, the combination of load-
ing resulting in the primary membrane
A07 stress in the shell is interpreted to be only
composed of the circumferential stress
from steam pressure. Sometimes, the stress
from the inertial loading is included in this
consideration.
c) In Section VIII, Division 1, it is very im-
portant to note that no formulas are given
for determining the stresses from thermal
A07 operating loads and pressure roll nip
load(s). Hence, additional criteria need to
be incorporated to establish the maximum
allowable operating parameters of the Yan-
kee dryer. Two such additional criteria are
based upon the maximum principal and
fatigue stress.
1) Maximum Principal Stress Criteria
A07 The maximum principal stress in aYan-
kee dryer shell is the sum of the stresses
that are simultaneously applied to the
shell and is always aligned in the cir-
A07 cumferential direction. The purpose of
these criteria is to recognize the paper
making application of the Yankee dryer
and to prevent catastrophic failure by
including all stresses. The ASME Code
does not provide specific formulas
for the full array of Yankee dryer shell
stresses encountered in tissue making.
A07
2) Fatigue Stress Criteria
Under normal operation, the stresses
due to the steam pressure, inertial and
thermal operating loads are considered
to be steady-state stresses. When act-
ing simultaneously, the sum of these
stresses must be judged against the
cyclic, or alternating, stress due to the A07
pressure roll nip load. Fatigue stress
criteria limit the alternating stress at a
given mean stress using fatigue failure
criteria described by the Goodman or
Smith Diagram. The purpose of this
limitation is to prevent crack initiation
in the outside wall due to the combina-
tion of stresses. As the thickness of the
shell is reduced, one or more of these A07
criteria will control the various operat-
ing parameters.
S1.5 PRESSURE TESTING
a) Water pressure testing in the field is not A07
recommended because of the large size of
Yankee dryers and the resulting combined
weight of the Yankee dryer and the water
used in the testing. This combined weight A07
can lead to support structure overload. Sev-
eral failures ofYankee dryers have occurred
during field pressure testing using water. If A07
this test must occur, the following review
is recommended:
The testing area should be evaluated for
maximum allowable loading, assum-
ing the weight of the Yankee dryer, the
weight of the water filling the Yankee
dryer, and the weight of the support
structure used to hold the Yankee dryer
during the test.
A07
so
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
A07 2) The manufacturer should be contacted
to provide information on building the
Yankee dryer support structure for the
water pressure test. Typically, the Yan-
kee dryer is supported on saddles that
contact the Yankee dryer shell at each
end near the head-to-shell joint. The
manufacturer can provide information
on saddle sizing and location so that
the Yankee dryer is properly supported
for the test.
A07 b) When pressure testing is desired to evalu-
ate the Yankee dryer for fitness for service,
an alternative to water pressure testing is
acoustic emission testing using steam or air
pressure. Typically, the test pressure used is
A q 7 the operating pressure. Caution needs to be
exercised to ensure personnel safety. Entry
to the test area needs to be controlled and
A07 all personnel need to maintain a safe dis-
tance from the Yankee dryer during the test.
^07 The steam or air test pressure should never
exceed the Maximum Allowable Working
Pressure (MAWP) of the Yankee dryer.
Acoustic Emmission Testing can be used to
locate and determine if a linear indication
is active, e.g., propagating crack. Metal lo-
graphic analysis is useful in differentiating
between original casting discontinuities
and cracks.
c) When nondestructive testing produces an
indication, the indication is subject to inter-
pretation as false, relevant, or nonrelevant.
If it has been interpreted as relevant, the
necessary subsequent evaluation will result
in a decision to accept, repair, replace,
monitor, or adjust the maximum allowable
operating parameters.
S1.6 NONDESTRUCTIVE
EXAMINATION
a) Nondestructive examination (NDE) meth-
A07 ods should be implemented by individuals
qualified and experienced with the material
to be tested using written NDE procedures.
ForYankee dryers, cast iron knowledge and
experience are essential.
A07 b) Typical nondestructive examination meth-
ods should be employed to determine
indication length, depth, and orientation
(sizing) of discontinuities in Yankee Dryers.
Magnetic particle, specifically the wet fluo-
A07 rescent method, and dye penetrant methods
are applicable in the evaluation of surface-
breaking indications. Ultrasound testing
is the standard method for evaluation of
surface-breaking and embedded indica-
tions. Radiographic methods are useful in
the evaluation of embedded indications.
B 1
NATIDNAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
SUPPLEMENT 2
SAFETY VALVES ON THE LOW-
PRESSURE SIDE OF STEAM
PRESSURE-REDUCING VALVES
S2.1
SCOPE
a) The subject of protection of vessels in steam
service connected to the low-pressure side
of a steam-pressure-reducing valve is of
considerable importance to proper opera-
tion of auxiliary equipment such as pressure
cookers, hot-water heating systems, etc.,
operating at pressures below that which the
primary boiler generating unit is operating.
b) To automatically reduce the primary boiler
pressure for such processing equipment,
pressure-reducing valves are used. The
manufacturers of such equipment have
data available listing the volume of flow
through reducing valves manufactured by
them, but such data are not compiled in a
form that the results can be deduced read-
ily. To protect the equipment operating on
the low pressure side of a pressure-reducing
valve, safety valves of a relieving capacity
sufficient to prevent an unsafe pressure rise
in case of failure of the pressure-reducing
valve, should be installed.
c) The pressure-reducing valve is a throttling
device, the design of which is based on
certain diaphragm pressures opposed by
spring pressure which, in turn, controls the
opening through the valve. If the spring,
the diaphragm, or any part of the pres-
sure-reducing valve fails, steam will flow
directly through the valve and the low
pressure equipment will be subjected to
the boiler pressure. To protect the equip-
ment operating on the low pressure side of
the pressure-reducing valve, safety valve(s)
should be installed on the low pressure side
of the pressure-reducing valve, which will
provide a relieving capacity sufficient to
prevent the pressure from rising above the
system design pressure.
d) In most cases pressure-reducing valves used
for the reduction of steam pressures have
the same pipe size on the inlet and outlet.
In case of failure of a pressure-reducing
valve, the safety valve on the low-pressure
side must have a capacity to take care of
the volume of steam determined by the high
pressure side and the area of the pipe.
S2.2
SAFETY VALVE CAPACITY
a) The capacity of the safety valve(s) on the
low-pressure side of the pressure-reducing
valve should be based on the capacity of
the pressure-reducing valve when wide
open or under maximum flow conditions
or the flow capacity through the bypass
valve.
b) By using the formula inS2.3 below, Inspec-
tors may calculate the required relieving
capacities of the safety valve(s) installed
on the low-pressure side of the pressure-
reducing valve.
c) Usually a pressure-reducing valve has
a bypass arrangement so that in case of
failure of the pressure-reducing valve the
boiler pressure may be short circuited
into the low-pressure line without passing
through the pressure-reducing valve. When
determining the required relieving capacity
of safety valves for the low-pressure side
of the pressure-reducing valve, the steam
flow through the bypass must be taken into
consideration.
S2.3 CALCULATION OF SAFETY
VALVE RELIEVING CAPACITY
a) When a pressure-reducing valve is in-
stalled, there are two possibilities of intro-
82
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
A09
b)
A09
A09
A09
A09
ducing boiler pressure into the low-pressure
system:
1) the failure of the pressure-reducing
valve so that it remains wide open;
and
2) the possibility of the bypass valve being
open.
It is necessary therefore, to determine the
flow under both circumstances in phara-
graph a) above and check that the size of
the safety valve under either condition will
be adequate. The following formula should
be used:
1 ) steam flow, W in Ibs/hr (kg/hr) through
the pressure-reducing valve
W = AKC
where,
A = internal area in sq. in. (sq. mm) of
the inlet pipe size of the pressure-
reducing valve (see S2.5)
K = flow coefficient for the pressure-
reducing valve (see S2.4)
C = flow of saturated steam through
a 1 sq. in. (1 sq. mm) pipe at
various pressure differentials from
Tables S2.3-a, S2.3-b, or S2.3-C.
(for U.S. Customary units) orTables
S2.3M-a / S2.3M-b,orS2.3M-c(for
metric units).
2) steam flow, W in Ibs/hr (kg/hr) through
the by-pass valve
S2.4
b)
K ( = flow coefficient for the bypass A09
valves (see S2.4)
C 1 = flow of saturated steam through
a 1 sq. in. (1 aq. mm) pipe at
various pressure differentials from
Tables S2.3-a, S2.3-b, or S2.3-C.
(for U.S. Customary units) orTables
S2.3M-a, S2.3M-b, or S2.3M-C ( for
metric units).
STEAM FLOW WHEN FLOW
COEFFICIENTS ARE NOT
KNOWN
It is possible that the flow coefficients K and
K 1 may not be known and in such instances
for approximating the flow, a factor of 1/3
may be substituted for K and 1/2 for K r
The formulas in S2.3 then becomes:
W = 1/3 AC for the capacity through the
pressure-reducing valve; and
W = 1/2 A 1 C, for the capacity through the
bypass valve.
Caution should be exercised when substitut-
ing these factors for the actual coefficients
since this method will provide approximate
values only and the capacities so obtained
may in fact be lower than actual. It is rec-
ommended that the actual flow coefficient
be obtained from the pressure-reducing
valve manufacturer and reference books
be consulted for the flow coefficient of the
bypass valve.
W = A, l< 1 C,
A09
where,
A, = internal area in sq. in. (sq. mm) of
the pipe size of the bypass around
the pressure-reducing valve
83
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
TABLE S2.3-a
Capacity of Saturated Steam, in lb./hr., per sq. in.
of Pipe Area
Outlet
pres.,
psi
Pressure-reducing valve in
et pressure, psi
1500 1450 1400 1350
1300 1250 1200
1150 1100
1050
1000
950
900
1000
76560 72970 69170 64950
60540 55570 49930
43930 35230
25500
950
77430 74180 70760 67000
63100 58770 53920
48610 42380
34890
24910
900
77750 74810 71720 68340
64870 61040 56820
52260 47050
41050
33490
23960
850
77830 74950 72160 69130
66020 62610 58900
54930 50480
45470
39660
29080
23190
800
75070 72330 69490
66700 63680 60390
56910 53060
48800
43980
38340
31610
750
69610
66880 64270 61260
58200 54840
51170
47080
42420
37110
700
66900 64270 61520
58820 55870
52670
49170
45230
40860
650
61550
58860 56260
53480
50440
47070
43400
600
58980 562 70
53660
51020
48470
45010
550
53810
51040
48470
45800
500
45850
450
45870
400
350
300
250
200
175
150
125
110
100
85
75
60
50
40
30
25
15
10
5
Where
capacities are not shown for in
et and outlet conditions, use the highest capacity shown unde
r the
applicable inlet pressure column.
TABLE S2.3M-a
Capacity of Saturated Steam, in kg/hr., per sq. mm of Pipe Area
pres.,
MPa
Pressure-reducing valve inlet pressure, MPa
9.75
9.50
9.25
9.00
8.7S
8.50
8.25
0.00
7.75
7.50
7.25
6.75
6.50
6.25
6.00
5.75
5.30
5.25
5.00
4.75
4.50
4.25
4.00
3.75
3.50
3.25
3.00
49.82
50.52
50.96
51.19
51.32
51.40
47.85
48.69
49.27
49.62
49.85
49.97
50.00
50.01
45.77
46.79
47.51
47.99
48.33
48.53
48.60
48.62
43.63
44.83
45.71
46.33
45.80
47.11
47.20
47.23
47.24
41.28
42.69
43.75
44.53
45.14
45.60
45.82
45.89
38.73
40.40
41.67
42.63
43.40
44.00
44.35
44.49
44.52
44.53
36.01
37.95
39.46
40.62
41.56
42.32
42.78
43.02
43.13
43.14
43.15
33.09
35.30
37.08
38.74
39.62
40.55
41.17
41 .55
41.75
41.77
41.82
41.84
29.47
32.33
34.46
36.12
37.51
38.56
39.44
39.98
40.31
40.43
40.46
40.48
25.37
29.02
31.59
33.59
35.25
36.63
37.62
38.33
38.81
39.08
39.10
39.12
39.14
20.89
25.31
28.43
30.83
32.82
34.48
35.68
36.57
37.22
37.63
37.74
37.82
37.88
20.46
24.45
27.53
30.04
32.05
33.52
34.64
35.50
36.07
36.33
36.45
36.48
19.36
23.13
26.20
29.37
31.16
32.56
33.64
34.41
34.90
35.12
35.13
17.64
21.90
26.41
28.59
30.01
31.66
32.65
33.39
33.76
33.81
18.76
23.01
25.72
27.84
29.51
30.76
31.60
32.15
32.45
32.47
32.48
Where capacities are not shown for inlet and outlet conditions, use the highest capacity shown under the applicable inlet
pressure column.
84
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
S2.5 TWO-STAGE PRESSURE-
REDUCING VALVE STATIONS
The safety relief valve for two-stage pressure-
reducing valve stations shall be sized on the
basis of the high-side pressure and the inlet
size of the first pressure-reducing valve in the
line. If an intermediate pressure line is taken off
between the pressure-reducing valves, then this
line and the final low side shall be protected
by safety relief valves sized on the basis of the
high-side pressure and the inlet size of the first
pressure-reducing valve. See Table S2.5.
TABLE S2.5
Pipe Data
Nominal
Pipe Size,
Unit Less
(ANSI
B36.10)
Nominal
Pipe Size,
Unit Less
(ISO
3607)
Average
Outside
Diameter,
in.
Average
Outside
Diameter,
mm
Nominal Wall
Thickness of
Standard
Weight Pipe,
in.
Nominal Wall
Thickness of
Standard
Weight Pipe,
mm
Approx.
Internal
Area,
sq. in.
Approx.
Internal
Area,
sq. mm
NPS 3/8
DN 10
0.675
9.53
0.091
2.311
0.191
124
NPS 1/2
DN 15
0.840
12.7
0.109
2.769
0.304
198
NPS 3/4
DN20
1.050
19.1
0.113
2.870
0.533
347
NPS1
DN25
1.315
25.4
0.133
3.378
0.864
562
NPS 1-1/4
DN32
1.660
38.1
0.140
3.556
1.50
973
NPS 1-1/2
DN40
1.900
50.8
0.145
3.683
2.04
1324
NPS 2
DN50
2.375
63.5
0.154
3.912
3.36
2182
NPS 2-1/2
DN 65
2.875
76.2
0.203
5.516
4.79
3113
NPS 3
DN80
3.500
88.9
0.216
5.486
7.40
4807
NPS 3-1/2
DN90
4.000
114.3
0.226
5.740
9.89
6429
NPS 4
DN 100
4.500
136.5
0.237
6.020
12.73
8278
NPS 5
DN 125
5.563
141.3
0.258
6.553
20.01
13009
NPS 6
DN 150
6.625
168.3
0.280
7.112
28.89
18786
NPS 8
DN200
8.625
1219.1
0.322
8.179
50.27
32530
NPS 10
DN250
10.750
273.1
0.365
9.271
78.85
51275
NPS 12
DN 300
12.750
323.8
0.375
9.525
1 13.1
73541
Note: In applying these rules, the area of the pipe is always based upon standard weight pipe and the
inlet size of the pressure-reducing valve.
BV
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
SB
Part 1 , Section 9
Installation — Glossary of Terms
99
NATIDNAL BOARD INSPECTION CODE • PART 1
INSTALLATION
PART 1, SECTION 9
INSTALLATION — GLOSSARY OF TERMS
9.1
DEFINITIONS
For the purpose of applying the rules of the
NBIC, the following terms and definitions shall
be used herein as applicable to each Part:
Additional terms and definitions specific to
DOT Transport Tanks are defined in Part 2,
Supplement 6.
A07 Accumulator — A vessel in which the test
medium is stored or accumulated prior to its
use for testing.
A09 Alteration — A change in the item described on
the original Manufacturer's Data Report which
affects the pressure containing capability of the
pressure-retaining item. (See sub-section 3.4.3,
EXAMPLES OF ALTERATION.) Nonphysical
changes such as an increase in the maximum al-
lowable working pressure (internal or external),
increase in design temperature, or a reduction
in minimum temperature of a pressure-retaining
item shall be considered an alteration.
ANSI — The American National Standards
Institute.
ASME Code — The American Society of Me-
chanical Engineers' Boiler and Pressure Vessel
Code published by that Society, including
addenda and Code Cases, approved by the
associated ASME Board.
Assembler — An organization who purchases
or receives from a manufacturer the necessary
component parts of valves and assembles,
adjusts, tests, seals, and ships safety or safety
relief valves at a geographical location, and
using facilities other than those used by the
manufacturer.
Authorized Inspection Agency —
New Construction: An Authorized Inspection
Agency is one that is accredited by the National
Board meeting the qualification
and duties of NB-360, Criteria for Acceptance
of Authorized Inspection Agencies for New
Construction.
Inservice: An Authorized Inspection Agency
is either:
a) a jurisdictional authority as defined in
the National Board Constitution; or
b) an entity that is accredited by the Na-
tional Board meeting NB 369, Quali-
fications and Duties for Authorized
Inspection Agencies Performing Inser-
vice Inspection Activities and Quali-
fications for Inspectors of Boilers and
Pressure Vessels; NB-371 , Accreditation
of Owner-User Inspection Organiza-
tions (OUIO) or NB-390, For Federal
Inspection Agencies (FIAs) Performing
Inservice Inspection Activities.
Capacity Certification — The verification by the
National Board that a particular valve design or
model has successfully completed all capacity
testing as required by the ASME Code.
Chimney or Stack — A device or means for
providing the venting or escape of combustion
gases from the operating unit.
Confined Space — Work locations considered A09
"confined" because their configurations hinder
the activities of employees who must enter,
work in, and exit them. A confined space has
limited or restricted means for entry or exit,
and it is not designed for continuous employee
occupancy. Confined spaces include, but are
not limited to, underground vaults, tanks, stor-
age bins, manholes, pits, silos, process vessels,
and pipelines. Regulatory Organizations often
use the term "permit-required confined space"
(permit space) to describe a confined space that
has one or more of the following characteris-
tics: contains or has the potential to contain
a hazardous atmosphere; contains a material
that has the potential to engulf an entrant; has
walls that converge inward or floors that slope
i do
NATIDNAL BDARD INSPECTION CODE • PART 1
INSTALLATION
downward and taper into a smaller area which
could trap or asphyxiate an entrant; or contains
any other recognized safety or health hazard,
such as unguarded machinery, exposed live
wires, or heat stress. Confined space entry re-
quirements may differ in many locations and
the Inspector is cautioned of the need to comply
with local or site- specific confined space entry
requirements.
Conversion —
Pressure Relief Devices: The change of a pres-
sure relief valve from one capacity-certified
configuration to another by use of manufac-
turer's instructions.
A07 Units of Measure: Changing the numeric value of
a parameter from one system of units to another.
Demonstration — A program of maki ng evident
by illustration, explanation, and completion of
tasks documenting evaluation of an applicant's
ability to perform code activities, including the
adequacy of the appl icant's qual ity program, and
by a review of the implementation of that program
at the address of record and/or work location.
Forced-Flow Steam Generator — A steam gen-
erator with no fixed steamline and waterline.
Inspection — A process of review to ensure
engineering design, materials, assembly, ex-
amination and testing requirements have been
met and are compliant with the Code.
Inspector — See National Board Commis-
sioned Inspector and National Board Owner-
User Commissioned Inspector.
Intervening — Coming between or inserted
between, as between the test vessel and the
valve being tested.
Jurisdiction — A governmental entity with the
power, right, or authority to interpret and enforce
law, rules, or ordinances pertaining to boilers,
pressure vessels, or other pressure-retaining
items. It includes National Board member juris-
dictions defined as "jurisdictional authorities."
Jurisdictional Authority — A member of the
National Board, as defined in the National
Board Constitution.
Dutchman — Generally limited to tube or pipe
cross-section replacement. The work necessary
to remove a compromised section of material
and replace the section with material meet-
ing the service requirements and installation
procedures acceptable to the Inspector. Also
recognized as piecing.
Examination — In process work denoting the
act of performing or completing a task of inter-
rogation of compliance. Visual observations,
radiography, liquid penetrant, magnetic par-
ticle, and ultrasonic methods are recognized
examples of examination techniques.
Exit — A doorway, hallway, or similar passage
that will allow free, normally upright unencum-
bered egress from an area.
Field — A temporary location, under the control
of the Certificate Holder, that is used for repairs
and/or alterations to pressure-retaining items at
an address different from that shown on the Cer-
tificate Holder's Certificate of Authorization.
Lift Assist Device — A device used to apply an
auxiliary load to a pressure relief valve stem or
spindle, used to determine the valve set pres-
sure as an alternative to a full pressure test.
Manufacturer's Documentation — The docu-
mentation that includes technical information
and certification required by the original code
of construction.
Mechanical Assembly — The work necessary to ^08
establish or restore a pressure retaining boundary,
under supplementary materials, whereby pres-
sure retaining capability is established through a
mechanical, chemical, or physical interface, as
defined under the rules of the NBIC.
Mechanical Repair Method — A method of A08
repair, which restores a pressure retaining
boundary to a safe and satisfactory operat-
ing condition, where the pressure retaining
boundary is established by a method other than
welding or blazing, as defined under the rules
of the NBIC.
1 D 1
NATIONAL BPARD INSPECTION CODE • PART 1 — INSTALLATION
NBIC — The National Board Inspection Code
published by The National Board of Boiler and
Pressure Vessel Inspectors.
"NR" Certificate Holder — An organization in
possession of a valid "NR" Certificate of Autho-
rization issued by the National Board.
National Board — The National Board of Boiler
and Pressure Vessel Inspectors.
National Board Commissioned Inspector —
An individual who holds a valid and current
National Board Commission.
Nuclear Items — Items constructed in accor-
dance with recognized standards to be used in
nuclear power plants or fuel processing facilities.
Original Code of Construction — Documents
promulgated by recognized national standards
writing bodies that contain technical require-
ments for construction of pressure-retaining items
or equivalent to which the pressure-retaining item
was certified by the original manufacturer.
Owner or User — As referenced in lower case
letters means any person, firm or corporation
legally responsible for the safe operation of any
pressure-retaining item.
Owner-User Inspection Organization — An
owner or user of pressure-retaining items that
maintains an established inspection program,
whose organization and inspection procedures
meet the requirements of the National Board
rules and are acceptable to the jurisdiction or
jurisdictional authority wherein the owner or
user is located.
Owner-User Inspector — An individual who
holds a valid and current National Board
Owner-User Commission.
Piecing — A repair method used to remove
and replace a portion of piping or tubing ma-
terial with a suitable material and installation
procedure.
Pressure-Retaining Stems (PRS) — Any boiler,
pressure vessel, piping, or material used for
the containment of pressure, either internal or
external. The pressure may be obtained from
an external source, or by the application of
heat from a direct source, or any combination
thereof.
Pressure Test — Prior to initial operation, the
completed boiler, including pressure piping,
water columns, superheaters, economizers,
stop valves, etc., shall be pressure tested in a
test performed in accordance with the original
code of construction prior to initial operation
of an installed unit that is witnessed by an
Inspector.
Repair — The work necessary to restore pres-
sure-retaining items to a safe and satisfactory
operating condition.
Re-ending — A method used to join original
code of construction piping or tubing with
replacement piping or tubing material for the
purpose of restoring a required dimension,
configuration or pressure-retaining capacity.
Re-rating — See alteration.
"R" Certificate Holder — An organization in
possession of a valid "R" Certificate of Autho-
rization issued by the National Board.
Safety Relief Valves — A safety relief valve is
a pressure relief valve characterized by rapid
opening or pop action, or by opening in propor-
tion to the increase in pressure over the opening
pressure, depending on application.
Settings — Those components and accessories
required to provide support for the component
during operation and during any related main-
tenance activity.
Shop — A permanent location, the address that
is shown on the Certificate of Authorization,
from which a Certificate Holder controls the A07
repair and/or alteration of pressure-retaining
items.
Testing Laboratory — National Board accepted
laboratory that performs functional and capac-
ity tests of pressure relief devices.
i 02
NATIDNAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
Transient — An occurrence that is maintained
only for a short interval as opposed to a steady
state condition.
Velocity Distortion — The pressure decrease
that occurs when fluid flows past the opening
of a pressure sensing line. This is a distortion
of the pressure that would be measured under
the same conditions for a non or slowly mov-
ing fluid.
/; VR" Certificate Holder — An organization in
possession of a valid "VR" Certificate of Autho-
rization issued by the National Board.
Water Head — The pressure adjustment that
must be taken into account due to the weight
of test media (in this case, water) that is 0.433
psi per vertical ft. (10 kPa per m.) added (sub-
A07 tracted) from the gage pressure for each foot
the gage is below (above) the point at which
the pressure is to be measured.
1 DZ. 1
NATIONAL BOARD INSPECTION CODE • PART 1 — INSTALLATION
i az.z
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